We get many calls for upgrades on this model,  as this car is becomming very affordable, 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!.

Search over 40,000 parts!
A huge parts info list for this car can be displayed here by choosing your exact year model or choosing a key word search

Typically this car is a “Subaru’s first serious model that grew into a cult following” it was the outcome of the turbo Legacy/Liberty era it has good value potential.
There are some great features of this car, 4wd, turbo 2.0 litre and most of all, a sensible budget with some carefully planned upgrades and it turns a great car into a bargain rad car!
(Editor note, this model is a very early option, and has ECU limitations against re tuning but with some simple mods makes this bargain model a sensible option for young owners)

The Air FLow Meter sensor on this model due to design and age is poor and can cause:
+ poor performance
+ piston failure
+ Bearing failure
+ poor fuel economy
+ see below for more info
Add the common mod of changing the air intake and you have a recipe for disaster….
Read on.

Can NOT be converted and tuned, using EcuteK Software.
Choose your tuner carefully, a plug in replacement is the only option

Bottom end and mid range performance can be dramatically improved with ECU tune. The engine is very detuned (as subaru dont want it to beat the STi ) and also limited due to emisions requirements when delivered by the factory.
Poorly designed upgrades magnifies the risk of piston failure.
Run too much boost or too much ignition advance and the result will inevitably be piston failure
Boost maps, can be improved.
Car should be run on 98 Ron Fuel unless a custom (ecuteK) map is done.
The turbo is OK and BIG. (much bigger than later model) but if over boosted with boost controllers etc can result in costly turbo failures.

On this model the aif flow meter sensor is the 2nd MOST UNRELIABLE (99 / 00 was the worst!) of all models and in 99% of cases is the root cause of most engine failures it can suffer contamination and in turn this will dramatically effect reliability and performance.
(see MRT for this solution)
The single rear exhaust O2 sensor if located incorrectly related to modified exhaust can cause problems, if old can also dull the cruise performance of the car and increase fuel use.
Crank, cam  and Knock sensors are reliable, but with age can fail.

Not worth considering.

Factory fitted unit is VERY SMALL dont fit a FRONT mount unless you plan a mosnter engine with resulting turbo to suit.
Use a better replacement MRT top mount, for solid improvements, this model offers the most improvement of ANY WRX or STi with a MRT intercooelr, but choose carefully.

Bigger injectors empty your wallet , tha factory ones are big enough for mods mods and add no power unless part of a E85 fuel retune.

Needs to be replaced with any mods over standard specification as by now they are tired and worn out.

(Some traps for people here, unless carefully chosen.)
Single scroll turbo engine pipes with split collector to fit wastegate is necessary and will add throttle response and is good value, with the correct complete design. High flow ceramic cat in the downpipe is best.
Flex joint is needed as well, with correctly located O2 sensor.
Get this wrong and the car will suffer CEL lights,  and cause poor fuel economy.
Consult MRT for this.

Other than a intake noise no power here.
MRT used to supply and fit Cold air intake and 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.
Do NOT change the air intake on this model, leave the factory airbox in place.

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, this model has a two and three part kit available.
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 factory fitted BOV is very small, the smallest of all WRX’s, so gains here are to be had.
The upside is adjustablity like a GFB Respons, or similar.

Be careful the OEM turbo is best kept in place as its simply HUGE unless you have the right other parts to match a new turbo upgrade.
As the limit becomes close to the engine depending on your choice turbo and will give no value unless you plan carefully.
(meaning if you fit a bigger turbo you can use its benefits but be careful as the extra boost will need to be tuned carefully )

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.
Best value here first and foremost is 2500 cc STi short block and or new Pistons and Rods.

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 first in the MRT XB kit as it will then have more power than the later 2009 model, and then some of my budget in 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 AFM sensor
  3. Check brakes
  4. Top Mounted Inetrcooler upgrade
  5. Exhaust upgrade.
  6. Boost controller OR new Replacement ECU (for even better results)
  7. New brake pads and discs if needed
  8. Front and rear sway bars.
  9. Front and rear sway bar links
  10. Positive shift kit.


No products in the cart.