I just got a 04 Pontiac GTO and i'm looking into giving it a bit more power.
HAVE IT COMPUTER / DYNO TUNES - CHIP IT - KN AIR FILTER AND PERFORMANCE PARTS SUCH AS DISTRIBUTOR, ETC.
longtube headers makes a big difference on these cars. that and a svede otrcai. also look into a set of 243 heads to replace the 241s that are on there. then go get a tune done. BUT if you havent replaced the radius rod or strut mount bushings yet you should look into replacing them with poly bushings before any power adders are done. it will make a world of difference. kollar racing is a great place to get the bushings. also if you have a manual look into a gmm or mgw short throw shifter.
best bang for the buck would be a good after market air intake, and a diagnostic tuner like diablo to maximize power, 700 bucks will give you up to 75 more hp
The only air intake system that doesn't suffer from heat soak raising iats on the 04 model is the svede otrcai. That alone is $500-600. That and a hand held tuner will not get you 75 hp....
for 75 additional hp heads and cam (more hp with compression and duration differences). CAI and tuner cost about 500-600 as chase said, but you will most likely get 10 hp, 15 hp if you are lucky. Headers, tuner, and CAI can take off 3-4 tenths of a second costing 1200-1700 that set up alone can get you 20-30 hp. With headers, HP dyno tune, and CAI on my 05 GTO, I have 370 rwhp at 400 ft lb of tq, which is about 30 rwhp gain. With the LS1 Look to drop 4000-6000 and have a completely different car that can run low and mid 12's in the quarter.
You can add a mostly reliable 150 hp for 700-1200 bucks. Easy install, but filling up the bottle adds to the cost.
Looking for a Used GTO in your area?
CarGurus has 474 nationwide GTO listings starting at $6,995.
Search Pontiac GTO Questions
Pontiac GTO Experts