1997 Jeep Laredo Backfiring?

What would make a Grand Cherokee backfire? It does it mostly when cold but can be random. When you first start to take off and when pushing on the gas, the engine seems to die out or something and if you push the accelerator further when it is dying out, it seems to backfire through the intake. It only does it once at a time unless I put the combustion cleaner through it. When I put the combustion cleaner through it, it read misfire #6. Today was the first time this happened: I was at cruising speed when I tromped on the accelerator and it seemed to go into neutral but was still in drive and after letting off the accelerator, it was fine and went into gear with no slippeage or anything! It has a complete fresh tune-up, new throttle position sensor, new crank position sensor, and new governor pressure regulator in the trans. This is frustrating me. The exhaust manifold has a small crack and you can here it a little when cold but goes away after it warms and the metals expand. I have taken it to a dealer and other mechanics but they found out it was a governor pressure regulator and fixed that problem but the hesitation and backfiring continued. The engine seems to hesitate more and backfire when I push the throttle while it hesitates or seemingly dies out, more when I added the mopar combustion cleaner and after I did the tune-up, it backfired a bit before the computer sorted things out. Please help as I am completely pulling my hair out. Thank you for your opinion. Also, when the engine seemingly cuts out, if I take my foot of the gas, the engine springs back into life. The engine does not wind out into high RPMS before shifting when the engine seemingly cuts out either. The trans seems to shift a little hard and when put into gear, it seems like I have to push on the gas a little harder than normal to keep it from moving until I want it to.