got an escort rs turbo running mfi system. its got chipped ecus. k&n. full stainless. front mount intercooler. kent cam kit. stage3 t3 turbo.

its boosting around 10 / 11psi and pulls like a train but when its getting up to the high revs it shudders, pops, bangs and give puffs of black reek out the exhaust. any ideas? ? ? ?