So I think I checked everything. I've been having this problem for a few months now. My jeep has a hard start, but idles fine. Also it wont go over about 1500rpm without backfiring through the intake and shooting flames out tailpipe, it is straight piped. I've replaced the full distributor, coil, plugs and wires, crank sensor twice, throttle position sensor, timing chain and sprocket and yes timing is right, tried a known good psm, IAC is working properly, no broken valve springs, went through the wire harness, all grounds have been cleaned still acts the same. Have a P0320 code that keeps coming back which is no crank reference to PCM. Can anyone help me or give me any ideas that I haven't tried yet?

 

Take a pic of your distributor wires. How is the distributor indexing sensor wires? How do you know you timing is right. What is your fuel pressure at the rail?

 

Shooting flames out of the tailpipe even!!

Well, if the code persists (after clearing) , the issue isn't solved. What brand CPS?
CAM and CPS failure can give similar symptoms.

 

The distributor and wires are correct, 100%. The index plug and wires are in working order. Continuity tested those and the CPS sensor wires. Fuel pressure at rail is 60psi running. Both CPS sensors I've put in are from napa auto, cant remember the brand right now. Currently a month out on OEM from mopar.

 

Unfortunately CPS still suspect though.
As I mentioned, faulty CAM sensor can give similar symptoms as a bad CPS. When mine went out, the exhaust smelled like fuel, perhaps explaining your flames out the tailpipe!

When replacing the distributor, did you have a new CAM sensor as well?