Im running the greddy kit with bluebox, stock fuel pump and stock injectors. Ran fine for a year, and after installing a high-flow cat, motor now hesitates/stutters at WOT after 5k rpms.

Before the cat install the motor would hesitate at high rpm on rare occasion but not as badly as now. And boost seems to hold at 7 psi while stuttering...

Do i need a new fuel pump??

 

hesitation is usually a sign of running overly rich. Do some Wide Open Throttle pulls and pull your spark plugs to see what color they are. It could also mean that you need to gap your spark plugs closer. When running boosted cars you need to bring the spark plug gap down so that you get a better spark while boosting 0.35-0.28 is the most common gaps

 

My car bogs when I go lean.

Nick