I have had my 03 wrx for a few months now and i am looking to purchase some performance upgrades. Were should i start and what makes and brands are best?
I would quite like to be sitting around 300 bhp maybe just over

 

to get 300+ bhp you will need to upgrade your turbo VF34/35 , STi TMIC, STi 550 injectors together with a decent panel filter, full decat (or sports cat) exhaust system and a remap. these mods should see you around 320bhp with simlar torque.

300bhp wont be achievable with your standard turbo

 

Yes, decent exhaust with decat/sports cat, panel filter and remap will get you around 280bhp. Will be a better drive than standard though

 

i have these mods on my bugeye, also upgraded the fuel pump to a walbro to be on the safe side. i managed 275bhp and 273torque, at just over 1bar.
you will do well to get 280bhp out of the standard turbo.

i have a few weeks old Afterburner Vortex back box forsale to get you started

 

280-290 is probs the most that can you can get out of the std turbo with a full decat system. Going over the 300 mark will require a turbo change and depending on how far over the 300 mark you go, sti injectors and tmic.

Obviously all with a remap.

 

is a turbo upgrade without changing the tmic and injuctors recommended? what gains are possable from this...say vf34?

 

You will not be able to run that turbo at proper boost tbh so will have to trim it back to fit in with what fuel can be delivered but the injectors.

Best bet is the get the turbo and injectors (and tmic) together if going the vf34 route.

You may just get away with fitting a TD05-16G with the current injectors for 300bhp if run slightly lean but it would be marginal.

The std td04 makes a great road turbo though and 280bhp is pretty lively ion the road in the real world.

 

cheers for the info duncan