Here's the deal. Took my '98 GT 5 speed to my mechanic to have a
Speedcal, a new power-steering rack, and an intake installed. While my
mechanic had the car the fuel pump took a dump so I had him replace it
with a high-flowing pump[Steeda part # 555-3050]. My mechanic puts it
all back together but now the car hesitates under moderate to hard
acceleration. The problem isn't very noticeable when the car is cold
but is pronounced when the car warms up. I told my mechanic what was
going on and he suggested changing the fuel filter. Did that but still
the problem persists. I'm thinking maybe it's a bad injector but I
don't know much about cars.

Any ideas?