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......

4500rpm is when the second butterflies should open.. Is it possible they are 'flicking open' due to using the wrong restrictor?

I no pro but i pretty shore you must keep 40psi at the injectors at all times, under 40psi the injectors will not pulse properly.I would contact ya local efi guy this might help also. All the best. Hope this helps.

check the coilpacks cause thats what mine used to do aswel. when you rev it while driving it would sorta kick and sputter around 4500 - 5000

thanks for the replies sorta reinfrcedwhjat i was thinking dattodude, i done have butterflies i have removed the plates and tiewired the rod so it cant move and is at its least restrictive i didnt bother removing the rod so i didnt have to weld any holes.is there any way of checking the coilpacks without getting new ones?