In my 91 when I got past 4000 rpm will stutter it doesn't matter the gear I check the timing and is all good I have 510 yellow too injectors small 16g turbo 2g maf , new spark plugs Ngk bpr8 good wires no codes any ideas what it could be? The computer is stock good caps not leaking I had 450 injectors and after I put the 510 is when it start to happen

Maybe one of th injectors are bad

Personally I've never met anyone that had their car run worth a sh*t with 510cc and a 2g maf without atleast having a safc to fine tune.

^ this.

you can not run your car like this. take everything off and put it back to stock. even the MAF

go to this website click email the man and ask him to burn you a chip for your cars needs.

all your doing right now is hurting your car. the ecu doesnt know how to automatically change its brain to match to what you add.

also go here click and start at the beginning of the 1G DSM tech guide. read everything.

BigD on these forums can burn you a chip too. He burned mine and it's been great.

Why the hell are you running bpr8es plugs? Even guys making 500hp rarely run those. With your mods I wouldn't use anything but stock Bpr6es plugs. Yours are way too cold and my guess is that they fouled out also.