I have never heard that one before. Sounds like a different problem or same problem you had but not fully fixed yet. Its got nothing to do with back pressure, I would like to know what fuel pressure is and what the mass air flow sensor is reading and youwill need a scan tool and fuel pressure gauge for that. My suggestion is to bring it back to the repair shop and let them try to rediagnose it. Hopefully they will not charge you for the diagnosis and if you think it might be a problem let them know your looking for them to get to the root of your original problem which you already paid to have fixed. Im not saying the coil cover or cat were not needed to be repaired but it sounds like something else is going on too.
Wednesday, November 12th, 2008 AT 8:23 PM