Keep getting a nasty misfire and once and awhile a backfire on acceleration. Compression test on all cylinders is fine and EGR has been changed. Plugs wires coil pack O2 sensors tps sensor and injectors have been changed and rechecked and rechecked and rechecked. Why do these codes come up if there is nothing wrong with these units?
Why can't my dealership find the problem using their scanner.Why do people keep telling me to check stuff that isn't associated with the misfire or a code associated with that type of problem.
Please don't reply to this if you are going to guess at the problem.

 

Certainly understand your frustrations but keep in mind the only thing you will get for your type of problem from someone miles or states away on a forum is an educated guess. There are many possible causes. Clearly they are having problems but considering your demand, a mechanic with hands on your vehicle is your best bet. Ask around for a competant mechanic.
http://www.obd-codes.com/p0300
http://www.obd-codes.com/p0306
http://www.obd-codes.com/p0404

Besides EGR did they check for vacuum leaks? Fuel pressure good?

 

Thats the best advice I got so far. It can be frustrating to put all these parts in and still come up empty. I would have saved a lot of money if I would have done that the first time.....trouble with me is I want the easiest way out and the cheapest but didn't understand that the cheapest way out is a real good mechanic.
Thanks again.