3800 wont start

[RebelDan]

i've got a 96 3.8 and i just replaced every gasket in my motor and when i got done i crunk it up and it run fine. the next day i put the y pipe on and went to crank it and it wouldnt crank it would just turn over and turn over and every now and then i get a backfire. its got compression air fuel and fire every basic thing a motor needs to run. i replaced the crank sensor plugs plug wires and it still wont crank. had the ingition module checked and it was fine. the coils are firin and so are the plugs and plug wires. checked the timing chain and it seems fine i replaced it a few months ago. the ses light is on and when i plugged in my obd2 reader it showed up with no codes and said the ses light wasnt on. anybody got any ideas as to what it could be?

[gpse3400]

might be bad MAP or MAF sensor...Normally somthing like this would point me to the ignition module being bad....But if it tested out, there isnt much left...