Backfires Crazy Like

Okay here I am again. Im wondering what causes backfires. I've got an 88 toyota 4x4, its got a 22re in it. I have done nothing to take care of the issue, but it backfires most of the time. Pretty much Always when im decelerating. Slowing down, seems to make it go *POW*. My friend told me its not bad, but I should get it fixed. Suggestions have been the timing, the spark plugs, or the exhaust system. Wondering if ne of you guys could help me narrow it down to one specific item. thanx

Timing is usually the problem with back firing. What you might also be hearing is your exhaust. Although, not as loud as a typical back fire. I've seen this issue with a catalitic converter that was the at the end of it's life.