past weekend i did a head swap on a 96GT with 99PI heads. the swap went great, just need to install the radiator fan switch to the intake manifold. some lights are coming on now and then.. grr. anyways big problem is that at first it wasnt doing this: when i stomp on the gas. it sound slike there is a misfire. but im not sure it is really as a misfire from the sparkplug or anything. its fast when RPMs are high and slow when RPMs are down. but lke i said only when i stomp on the gas. does anyone know what it could be or soomeone who has a 96GT and swapped PI heads on their car had this problem? thanks!