I am doing some minor mods on my 02 gt. I have added a bbk cai and now looking at a new plenum and throttle body. My question is do they make a noticable difference in hp or throttle response. Then which ones are the best to buy?
You could get longtube headers with an of road x or h pipe to increase power a bit or get a nitrous kit installed for a 50 or 75hp shot. Other than that forced induction is only choice for making good power for a reasonable price.
After gears, FLSFCs, offroad midpipe (if that's an option in your region due to emmisions laws and standards), or cat back, think forward about your forced induction install. Its never too early to upgrade your fuel system with a better pump or a Boost a Pump. Its nice to have support mods in place that not only strengthen your existing performance but leaves you ready to easily step up to the next level.
Never a bad idea to have some nice rims and sticky tires. Even in stock form, these cars benefit greatly from added traction.
My .02, in no particular order:
blower
blower cams
tune
injectors
fuel pump
fuel rails
throttle body
MAF sensor
long tubes
h or x pipe
muffler with turn downs
Then, get the suspension dialed in.
Other than that, anything else you will need some major head/block/internals work.