engine chugs and stumbles upon acceleration.
I have replaced egr valve, air filter and sprayed throttle body cleaner into running engine. all these measures seemed to solve the problem for awhile. Symptoms reappeared immediately after putting in6 gallons of fuel yesterday. I'm replacing fuel filter in a few minutes. I'm wondering if there might be a more likely cause for this frustrating problem in an otherwise good running 5.7L motor. Any suggestions would be appreciated.