If by buck you mean the car pitches forward violently during a WOT run usually in the top of a higher gear (like 3rd or 4th) then you are hitting fuel cut. This isnt just really bad sputtering...the whole ignition system is shutdown when you hit fuel cut and the engine just shuts off (which is very scary the first time it happens when in gear at WOT).

If it just acts like a bad sputtering (or miss) at high RPMs then you are probably getting MAF overrun (but a miss is just an indication of lack of fuel or ignition). How many honeycombs have you removed if any? With that turbo you should be very close to overrunning the MAF (if its unmodified) even on 15 psi.

The AFC wont help either condition...BUT you can install larger injectors and compensate with the AFC. Youll still need to mod your MAF or switch to a 2G MAF to get around MAF overrun. Youll also be able to see your Karhman counts on the AFC so youll be able to tell exactly how close to MAF overrun youre coming.

Id try rewiring the pump (from the VFAQ)...that helped my top end quite a bit. Then pull some honeycombs out of the MAF (if you havent already). Last resort is really injectors and AFC but you will need them anyway to run real boost at the track.


------------------
John
90 Talon TSi AWD
2KW K4U