troys98gt

i have a 98 gt 4.6 it wont run, when i try to start it it backfires and blows the air hose off the map sensor, i first found out that if i took the passenger side coil pack off it would run on 4 cylinders without backfire, once reattached it would backfire. so i changed the coil pack and got the same result, i then tried a new crank sensor and still got backfire. im gonna try the harmonic balance (crank damper) to see if it has shifted. im at a loss right now and dont know what else to check, if anyone has any input on this subject or have heard of such a problem i would greatly appreciate it .

thank you,
troy