Either a flash or your hitting fuel cut from overboosting.

 

this is what i am thinking but i'm waiting for some funds so i can get a shop to check out the problem.

 

if you were hitting boostcut you would feel like you hit a wall its not subtle at all.. maybe your tuner mixed up stationary revlimiter with the regular one... go hit the stationary one and see where that is at...

 

just get a tuner to look at it