98 Sunfire Baffling Problem...

Hi. My 1998 Pontiac Sunfire, 2.2 , has been having a problem which we have yet to figure out. The car will hesitate when accelerating either from a complete stop or at times while driving. The hesitation can vary from day to day. At times it will feel as if the gas is not being taken up and have a slight hesitation. At other times you may feel the hesitation in the form a shudder(ing) while accelerating and/or in which the vehicle will buck...sometimes slightly, sometimes bucking quite hard. The hesitation stops completely upon release of the gas pedal or if you floor the gas pedal.
This can happen on a daily basis and sometimes does not happen for a day or two. It can be random. It started this spring.
I have had the oil changed, fuel filter and air filter changed, new ignition wires and spark plugs as well as the 1 and 4 coil replaced. (We have also replaced the water pump and alternator in the last year.)
Does anyone have any ideas on what it could be? I'd appreciate any help.
Thanks!

There are a couple items I would recommend that you check. First, check the fuel pressure to see if it is at the proper level especially while you are revving the engine. If not replace the FPR. Next, check the ignition module it may be causing your problems in not transmitting the proper signal to the coils when necessary. Lastly, you may have bad fuel injectors. I had a V6 that acted like it had a potato in the tailpipe. If it put it in a lower gear it would run fine. This may be your problem. Hope these suggestions help.

Sounds similar to problem I had with the family truckster (TransPort)

The EGR valve was bad/plugged.