So you don't know exactly what the car is doing, and you don't know if it's backfiring through the throttle body or not.. I see this going somewhere fast.
If it hasn't had a tune-up anytime in this era, check the plugs, wires, maybe the AFM or TB if they're dirty, air filter.. etc. You can at least check that yourself and report back... hell, maybe even drive it and give us a better description of the problem.