Ive had this issue for a while, but had other things I needed to address first. Was hoping it'd go away. But seems after fixing the rest of the issues this still remains.I just replaced my crank pulley with the ATI unit. Replaced fuel pump and filter, and replaced cracked intercooler boots.

Basically if I make a hard redline pull from 1st gear, after i cross around 4k rpm the acceleration starts to waver and bounce a little on the way from 4k to 6500. I have a scangauage2 and need to see if i can get a boost readout on it. If so I'll try and watch my boost during the hard pull and see if it fluctuates

Any other thoughts or ideas? Anyone else experience this? I've heard of yoyo from bypass, but isnt that normally partial throttle around 2-3k rpm? This is WOT after 4k

 

bypass valve , maybe popped a vacuum line