Cutting out after Apex exhaust installed!!!

[jawsgst]

Ok i have a FPBig28 turbo, Intercooler pipes top and bottom and Greddy BOV and just installed my Apex N1 exhaust and DP today. The turbo seems to start pulling harder than hell around 3.5k rpm but around 4.5k rpm it starts cutting out like hell and backfiring out the tail pipe. It cuts out then pulls again then cuts out again. Is this fuel cut? If not what could be going on?!?! Please help!

 

[jawsgst]

Also this only happens under WOT, if i stay out of the gas enough that the turbo isn't completely spooling up then it won't cut out. It cuts out pretty hard but not as bad as some make fuel cut sound. Could this be an exhaust leak. I am running stock boost levels because i don't have a controller. I am about to order a 255lph fuel pump and see if that might help. Any ideas, feel free to post!

 

[GSX20]

It's fuel cut. It's because you upgraded your exhaust. You increased your exhaust flow and now the wastegate can't bypass enough of it fast enough. I got the same problem right now. Looks like porting is in our futures.