I have a payne model 394gaw036050 heater. The problem is intermitant and when i try i can not repeat it. I hear a boom noise coming from the heater and in the past have seen a flame shoot out of it. I was told that it is the auto-lighter and have changed it at least three times over the past four years.

I believe the booming is coming from the gas for the pilot light and not the main line because i am still here. Any ideas on what's wrong and what i can do?

That is one old furnace you have. Dirty pilot or burners will do it. The gap on the sparker being wrong or the wire going to the sparker going bad will cause it. It may be time to have this system serviced and a good once over.