[desertmike1]

I have a 98,
Sense day one, and after cold start only, it does a pop pop in the exhaust. I have never had a check engine lite (knock on wood)
Many differant problems will cause your missfire, vacuum leak, improper fuel delivery, leaking EGR valve, ignition system ect.
There is no simple answer, you might start out by just giving your engine a good look over for possible loose hoses, wires, components ect.
Buy a can of carb cleaner, and carefully spray around all of your induction starting at the air box and moving in toward the intake manifold to cylinder. Be carefull, the carb cleaner is flammable, so avoid spraying things like ignition coils, alternators, and exhaust. I would do this on a fairly cool engine.
If you spray across a leak your engine RPM will rise momentarily.

This should be a good start.

-Mike