97 Lumina Backfire

HI how bout a little help. My daughter overheated her 97 Lumina 3100, the heads were warped so I had them repaired. I reinstalled everything, started it up, it had a little valve noise and a little of a rough idle, then the throttle stuck, shut it down, throttle stuck again, shut it down. Now I have an intermittent backfire through the intake. Removed the upper intake checked my bolts on the lower intake, put silicone on them, but it back together and I still have a rough idle, with backfire. Any advise? Thank Cliff

Welcome to AF, first thing comes to mind is one of the pushrods was swtiched this can cause a bent valve and the backfire, thru the intake I assume? Compression test the engine, check plug wires for the right order also.