So my car has been doing this for a while, not sure what's causing it, can't remember if it has always done it or not.
So, in 5th gear, from 2000 rpms on up, if you mash the throttle down suddenly and hold it, you get a "boost surge" to 17psi, the a taper down low, then a surge, then a taper, then it surges back and holds steady. Only happens down low in 5th, no other gears.
Also, doesn't seem to happen or as noticeably when the ambient temp is below 75 deg. Today when the vid was shot it was super hot, 100deg which is when it is the worst.
If instead of WOT you roll to part throttle boost, it'll build 5 lbs and hold steady till red line.
Again only happens in 5th, I hit boost targets in all other gears. Also only an issue when you roll on from a low RPM in 5th as well.
Stock turbo (still in great shape)
Stage 2 protune (done in 07)
Full TBE with CATCO CAT
Stock catless UP
Car is super sound mechanically, with newer clutch, timing belt change, etc.
Only thing I have never done is removed and cleaned the TB.