Slow acceleration after intake and exhaust

Jordo!

Probably something isn't bolted down well, and the MAF sensors are moving around under load.

As a consequence, you will get MAF sensor misreads, which may be telling the ECU to add too much fuel.

That would correspond with being down on power and blowing out black smoke (i.e., unburnt fuel).

Other possibilities include damaged MAF sensors (unlikely) or a vacuum leak somewhere either before or immediately after the primary O2 (quite possible).

Whatever is causing the noise (hopefully not actual engine knock...) may be alerting the knock sesnor to pull timing.

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henry0844

thanks for the info. like I stated before I'm going to go to Stillen and get an uprev tune and get the car looked over. just today I heard a kind of squeaky tick sound coming from the drivers side of the engine bay. increased in sound with Rpms. I really hope I don't need to go to nissan for warranty work.