What is wrong with my ford bronco?

i have a 1989 full size ford bronco with the 5.0... when it is in park/neutral it runs/idles fine and has no bad sounds or problems... but when its being driven it tends to jerk forward and it pops through one of the air filters and it sounds like the fuel pump isn't keeping up with the motor...thinking it was too much back pressure due to clogged catalytic converters i recently had the cats and muffler replaced... a mechanic told me that its probably not a fuel delivery issue because when we drove it he smelled plenty of fuel... plus the fuel pump primes every time the key is turned on... im hoping it does not need a valve job... any ideas? thanks : )