boostin problem need help badly

aight my car boosts fine until it hits 4500 rpms. then it starts sputtering and will sputter every 500 rpm's after that. but this only happens when i floor it. if i let it build boost slowly it's fine. some ppl said maybe plugs and wires but i changed both of those already and it didn't change anything. someone also said maybe fuel cut, but i have a walbro fuel pump and rc 550cc injectors. and it never did it before. the only thing i can think of is that i need to tune my afc cuz i'm gettin' 11mpg on my 97 gst right now. also another weird thing is that it'll start sputtering once it hits 1.5 bar, which is 22psi i kno and that's wut it use to run. anyone have any ideas of how to fix this?

Check for a boost leak.

really? alright i'll do a boost leak test on it sumtime this week

Also what do your plugs look like?  You could also be running way rich.

First of all yes im running way rich, and I gave my buddy a ride in it so he could feel the sputter. And of course it didn't sputter a single fu***** time. I was so pissed and confused at the same time.

change the plugs with NGK classics and change the wires with OEM wires

Well I have bpr7es plugs in there with oem wires. Got any other ideas?lol

maybe the plugs arnt properly gaped. I know it seems like you ruled them out but i cant think of anything else that would cause this. Could possibly be the rich though. Do you have a wideband. Cuz if not you really need to get it

It cant believe it would be the sparkplugs, even after changing them. And besides how would it go away once my buddy gets in, its weird. And yeah emonz has been trying to make me get a wideband for the longest time now but im broke as a joke and can't afford one,lol unless sum1 wants to donate one for a good cause, there's nothing else it could be? Cuz I will change the plugs again if that's all it can be. And yeah I gapped them to 0.032

i would just turn down the boost for now to be safe. Is the SAFC zero'd out or is it actually set on a tune

Its zero'd out right now, mike gave me sum numbers to try and well see if it makes it any better. And the boost is turned down (did it today)