hit a big bump now won't start

i have a 1992 100CS automatic (not quatro). the car just a few days ago had a fuel pump and filter replaced. it ran fine...until now. i was going downtown and hit a large pothole (there is construction and they are tearing up the roads). after i hit the pothole it continued to run fine for about 10 minutes. after that i noticed it was running kind of rough and didn't accelerate quickly or seem very responsive. that continued for about 5 minutes. then i parked the car and turned it off. when i turned it back on it started but ran very rough and the rpms lowered. that continued for a minute and then i shut it off and had it towed home. i checked to see if it was the fuel pump and there was pressure in the lines. i looked under the car and i see where something hit, but it hit the frame, not the fuel pan, exhaust, or such. i don't know what happened. any help would be appreciated. thanks -jason