What are the most common upgrades that increase hp, and speed? Had 03 cobra and we had small little upgrades that gave good hp and speed.

 

trade it for a 450 or 460. Seriously, there are very few performance parts for any model of the 3GS and I have yet to see any proof of noticeable gains. You can get them to make different noises and look different, but I don't recall seeing any dyno comparisons.

 

your cobra is FI car, it's always easy to tune FI cars

on the gs350 (or all lexus in general), there isn't really any mods for significant gain