what size turbo would be on an 04 WRX ?

 

You have a TD04, its small, capable of about 280bhp(ish)

Tony

 

any point fitting a TD05,would i gain anything?

 

Yes, its capable of about 70bhp more, tops out about 350bhp, but you need supporting modifications, look at the brakes, standard suck so disc's and pads minimum, injectors need upgrading, as does the induction (panel filter) and exhaust system, also an uprated fuel pump, uprated top mount and a remap.
Be warned this will push your clutch to the limits and also it will be top end for reliability on your engine (and your gearbox may suffer, depends how it gets used)

Tony

 

so far i have...green panel filter
prodrive sports cat + downpipe
walbro fuel pump
NGK 7's
Bob Rawle remap.

would i need sti injectors,tmic + a remap?

 

Yup, those would suffice

Tony

 

But you say it will put a major strain on engine ,clutch and gearbox.Not worth all the hassle then?

 

Well its about as far as you want to go mod wise, after that your looking at an STI if you want to mod any further without issues.

Tony

 

I think i will leave well alone and turn my attention to the suspension and brakes. I already have two perrin arb's to go on looking for lowering springs to go with them.Do you know if sti and wrx springs are interchangable,what make should i be looking for or are they pretty much the same?