Backfiring Problem here

Here is the problem.I have a 2000 Jeep GC Laredo 4.0. I thought I might of had a cracked head gasket because of the overheating and compression tests I did. So I replaced the head gasket, finished the job. Then when I went to start it,it starts fine, but backfires through the throttle body now. It sounds like a timing issue, but there is no way, because I didnt even take the timing cover off. The only thing I did was take the push rods, rockers, fulcrum and bridges off, and seperated acordingly to where they go back. When I put it back to gether, I put the #1 cyl at TDC and then installed the hardware and torqued everything to specs. Should I have put every piston to TDC when I put the hardware back on instead of just doing the #1 cyl? Is there any tests I can do to see if its out of timing, I am afraid to start it because It might catch fire or bend a valve or something like that. any help would be great.

Did you correct the distributor when you turned the engine over to #1?

it is a distributerless system. Has the coils. Thats what me and my dad was thinking, but its a coil system. I know when I had my old race car, it would backfire through the carb, and that was because of the timing. The only thing I think of is when I turned it to TDC at,there might have been slack in the chain, and it jumped a tooth. But it starts up fine. This thing is killing me.