my engine is getting rebuilt at the moment and im thinking of things i can fix while its out when i used to rev my engine not free revving but driving,i used to get like a fuel surge type sensation at revs above 4500 or so, im just trying to figure what it could be i used two different types of plugs stock and platinum, it has a new vl fuel pump and cleaned injectors running stock boost 8psi could this be my coil packs going or could there be a fuel issue i have sard reg set at around 40 psi drops to about 38 when u rev it,also the fuel pickup is at the rear of the tank and it has 3/8 fuel lines with decent return and please nobody ask if i had a full tank . anyone got any ideas......