We get many calls for upgrades on this model, as a guide to assist you we have created this list to save your time, guarantee your money is invested correctly and most of all give you maximum value!.

Typically this car is a “Subaru’s Grand tourer solution to the poorly released and badly tuned B4 TT” a high performance family car that is detuned when compared to the Impreza WRX and STi models.
There are some great features of this car, stealthy “revised” looks (compared to the past twin Turbo model), 4wd, turbo 2.0 litre and most of all, a sensible budget with some well planned upgrades and it turns a great car into a potential Impreza STi beater!

This car is full of traps for the poorly modified options.
Its the only twin scroll turbo car ever sold in Australia by Subaru and as a result its poorly developed by many workshops.
Put simply the engine is a cracker, the turbo TINY.
FIt an exhaust at the wrong time and with bad ECU tuning or boost controllers, the end result will be a $6000 turbo repair!

(All Australian models 2004 – 2006 )
Can be converted and fully tuned, using EcuteK Software for almost any improvement, ECU is a new designwhen compared to the previous model and allows solid results with correct settings and allows good improvement.

Bottom end and mid range performance can be dramatically improved with ECU tune. The engine is detuned (as subaru dont want it to beat the STi) and also limited due to emisions requirements when delivered by the factory.
Strong factory fitted fully forged pistons and HD rods are reliable.
The overall weight of the car makes the car FEEL slow, but when upgraded correctly the Engine can deliver reliable results
Poorly designed upgrades  magnifies the risk of turbo failure.
Boost and VVT cam maps, can be improved.
Car MUST be run on 98 Ron Fuel unless a custom (ecuteK) map is done.
The turbo is reliable, but if over boosted with boost controllers etc will result in costly turbo failures.

On this model the air flow meter sensor is reliable, but can suffer contamination and in turn this will effect reliability and performance. (see MRT for this solution)
The twin rear exhaust O2 sensors if located incorectly related to modified exhaust can cause problems, if old can also dull the cruise performance of the car and increase fuel use.
The BIG issue on this model with sensors is the rear O2 sensor that is prone to early wear and tear and typicaly needs replacing every 2 years
Crank, cam  and Knock sensors are reliable, but with age can fail. 

Not worth considering as the interceptors simply do not have enough options to tune and modify the latest technoplogy control inputs.

NEW (replacement) ECU
Factory ECU retune is best value unless a really serious engine rebuild is chosen.
See notes above

Factory fitted unit is good, dont fit a FRONT mount.
(Unless you plan a big turbo and for that you will need a new engine)
This model has a revised design that requires careful planning with the right parts that done correctly can deliver improved results on hot days.
Use a better replacement top mount, but choose carefully.
Contact us for a specifically designed TMIC (Top Mounted InterCooler) that MRT manuafactures for this model.

Bigger injectors empty your wallet and add no power unless part of a E85 fuel retune or major engine rebuild.
Save your $$ for suspension and get some GOOD improvements.
OEM Injectors are big enough unless you do a major engine rebuild.

More than adequate up to 50 kw at the wheels after that a 500 hp pump can be retofitted

(Some traps for people here, unless carefully chosen.)
Twin scroll turbo engine pipes with split collector to fit wastegate is necessary.
BUT the turbo is so small, a larger exhuast will add NO POWER.
The risk is turbo failure due to the reduced back presuure
An exhaust ONLY ads noise with this model and should only be changed when matched with a turbo upgrade like the MRT XC Power kit
Flex joint is needed as well, with correctly located O2 sensor.
Get this wrong and the car will suffer CEL lights, deactivate the Cruise control and cause poor fuel economy.
In some cases depending on final tune the twin mufflers in sedans can be re used with a complete exhaust, consult MRT for this.

Other than a intake noise no power here.
MRT used to supply and fit ram pod style intakes, but with technology and recent testing and on the later models these were made redundant. The positive intake pressure with the factory intake is best kept in place.
A replacement panel filter in the std airbox will save on future servicing but give no power improvement.

Items such as aftermarket plug leads, high capacity discharge ignition systems etc all will ad very marginal if any improvement.
A GFB alloy pully kit will fit some models, but this varies as this model now has stretch fit belts and no adjustment like earlier models.
If fitted a kit or alloy crank pulley will result in snappy throttle response.

A replacement Blow Off Valve will add to a snappier throttle response, but give no increase in peak power. Run externally venting and the occasional CEL will occur with the downside of poor fuel economy.
The upside is adjustablity like a GFB Respons, or similar.

If you have the budget a turbo upgrade will add power, but be careful the OEM turbo is best kept in place unless you have the right other parts to match a new turbo upgrade.
Get this wrong and you will destroy your turbo.
As suggested above ONLY fit an exhaust and modify the boost if you genuinely known what you are doing
The right choice of turbo will give good value as per an example in the MRT XC power kit.

Like above if you have a solid budget, then a rebuild will give some great and huge benefits, but a rebuild will cost over $7k and then you need to choose carefully there are many options, but only if you REALLY want to as the engine is damn good.

Is the car serviced correctly? Because often a service by a workshop who really knows subarus will be your best choice for first place for power and reliability.


  • Upper engine cleaner and in tank fuel additive. (when was this last done, its a subaru suggested option).
  • Good quality low friction engine oil such as Mobil 5 w 30 will give around 5 kw and better fuel economy over a non synthetic oil.
  • Fuel system service, MRT offer this and often get good results, cleans the EGR “gunk” out of the intake and combustion area.
    Also injectors as well as inlet manf and exhaust as well as fuel pump, lines and sensors.
  • Synthetic trans and diff oil, again like engine oil this adds up in benefits.
  • Timing belt, fuel filter are again areas that should be checked and renewed.

check out the performance / suspension section for REAL gains and benefits.
If I owned this WRX suby, I would invest some of my budget in the MRT XB kit and then brakes and suspension as this is guaranteed BEST VALUE!
more here https://mrtperformance.com.au/performance/suspension

Refer the MRT vehicle service section here and take advantage of our free 78 point check to ensure your car is in top shape!


  1. Check service history.
  2. Check the O2 sensor
  3. Check brakes
  4. ECU upgrade and re tune.
  5. New brake pads and discs if needed
  6. Front and rear sway bars.
  7. MRT XB kit
  8. Front and rear sway bar links
  9. Positive shift kit for 6 speed models
  10. New Top Mounted Intercooler.


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