That's dangerous . Usually your 1st upgrade if you're planning on turning up the boost is an aftermarket boost gauge. The stock one is as worthless as they come. I would absolutely run wastegate pressure until you have a boost gauge. It could be fuel cut if it feels like you're hitting a wall. A boost leak is common too. The added cfm of the bigger turbo could have blew something loose.

You should definitely get an AFPR if you're planning on keeping that 255lph pump in there because it can overrun things easily. I doubt that's 100% your problem though, but a boost leak+unaided 255lph fuel pump could definitely cause too much fuel to be dumped (even with stock injectors) which would flood your cylinders and cause it to misfire as well.

Get it back to wastegate pressure and see how that goes. If you're still having problems do a boost leak test, and if you fix all the leaks and it's still doing that then I'd replace the fuel pump with stock or 190lph or get an AFPR set-up. Good luck!

NATAS said:

You should definitely get an AFPR if you're planning on keeping that 255lph pump in there because it can overrun things easily. I doubt that's 100% your problem though, but a boost leak+unaided 255lph fuel pump could definitely cause too much fuel to be dumped (even with stock injectors) which would flood your cylinders and cause it to misfire as well.

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this is true, the same thing happend to me. too much fuel is not a good thing

Ill diffently look into those and check over everything. my other question i guess would be. Is how much boost can the stock injectors handle? I havn't bought the car yet. So how much damage do you think could of been done if its dumping to much fuel, or has a boost leak?

I've got a 16g turbo on an 1991 gsx and I don't have any problems with the turbo size diffrence. I'd put my money on a boost leak.