do you live close to an auto parts store that does testing on ignition modules?? my 94 was backfireing like a mother f'r about a year ago and i called around and everybody said it wasnt the ign module cause the truck still ran so i put about 150 bucks into it before i gave up and just bought an ignition module and that was my problem. mine was backfireing out of exhaust and tbi. mine idled a little rough like there was a slight miss too. hope this helps ya out.
ps i know mine was backfireing out both cause you could hear a muffled backfire from tbi and then a backfire like a shotgun went off inside the truck cause i had true dual pipes with no glasspacks on it at the time