If l modified a WRX with a performence exhaust system, cold air intake, and some sport suspensions would it be just as good as an STI?

Most likely not, like the ST l is turbocharged and so is the WRX l think but l doubt it.

no, ST l is better than a normal one with modifications so just buy a subaru wrx sti if you have money.And the ST l is already self modified so you will not waste money on accessories

l doubt bolt ons will make that much of a difference.

Nope.

If you make the boost 5psi higher along with those modifications you listed plus an aftermaket performance intercooler, then it would be as good as the STI.

Forget the cold air intake; add exhaust, tune, & suspension & you're probably 90% of an STi.except for brakes.

http://sportcompactcarweb.com/roadtests/0308scc_tuned_subaru_wrx_vs_sti/index.html

http://sportcompactcarweb.com/roadtests/0308scc_subaru_wrx_sti_track_acceleration/index.html

http://sportcompactcarweb.com/roadtests/0308scc_subaru_wrx_sti_track_acceleration/index.html

http://sportcompactcarweb.com/roadtests/0308scc_subaru_wrx_sti_turning_stopping/index.html

If you consider the AVCS, bigger turbo, Brembo brakes, 6-speed bullet proof tranny, HID lights, better wheel bearings, wider and lighter BBS wheels, stiffer suspension and the Driver Controlled Center Differential a slight difference then l suppose they are similar. But the 65HP difference is very easy to make up, especially with the 06 and up WRX's.

The wrx is a great car in & of itself, but in a word no, not without quite a few mods or a fullout swap.
As stated before, the ST l gets a lot of extras not just a simple bump in HP. Engine wise the advantages it get r AVCS (valve control) bigger turbo (older STIs use VF39s newest one a VF43) forged rods & crank (pistons r cast), mated to a 6spd tranny with DCCD (controlable center diff for torque split setting). It also rides on better suspension with larger Brembo brakes.

A common mod for WRX is has been swapping out the small TD-04 for the ST l VF39, then a protune or ecu reflash. It is really not that hard to upgrade WRX is over stock ST l power, but even then u lose out on a lot the ST l has to offer, low rpm grunt AVCS gives, launch control, Brembo brakes & the close ratio 6spd tranny with diff control (WRXs r known for having ''glass'' trannies at around 300+hp, but a large debate is whether u drive like a tool or not)

Do not let this deter u though, WRXs r still great cars & a lot of fun, they're also a lot cheaper. l kind of do regret not buying an ST l for the very reasons stated above, but cost & the situation would not allow for it. Rest assured I'am by no means unhappy with my purchase though. Just do not think of it as '' l gotta beat an STI'' because guess what? u should buy an ST l then.

No. But if you do modify a WRX like this then be careful that you do not get hammered for insurance. A modded WRX might cost more to insure than a standard STI, even if its not as fast.

Depends on what year STi and what year WRX. l was reading in car and driver that the new wrx is faster to 60 then the older STi's. This is due to the extra 41 ponies that are under the hood. So When you ask is the new WRX better then an older STi.the answer is yes. Of course if you are comparing the same years the STi is have always been the next level in the Impreza lineup.