car not running properly

where in the exhaust is it popping ? from the rear tailpipe or in the engine bay ? if in the engine bay, you may need exhaust manifold gaskets + the exhaust "donuts " that join the manifold to exhaust. as far as pinging. start by using up the fuel, adding premium ( despite what factory car sales tell u, these cars need higher octane ) first change the fuel filter and then b4 filling: add a bottle of gas dryer + a bottle of fuel inject cleaner. as far as other pinging. recheck the timing is spot on. otherwise start checking ,smog air check valves located on side of engine near the exhaust ports.

Sounds like it is out of time...verify the marks on the balancer haven't "slipped" (5.0L are notorious for this, leading to symptoms such as yours if timed incorrectly). Base timing is 10 degrees factory, with the timing SPOUT connector removed.

also could be a burnt or bent valve.

along w/ my prior recomm, i totall agree w/ checking balancer / timing. i just went thru that and replaced a module and coil. toss the distribrutor if its old and high mileage. also : is there missing whenthe rpm's increase? thats a sure sign of the above. stever2009

Do you have a 5.0 H.O. Roller 302 EFI or a regular 5.0 302 TBI ? They do have different firing orders and if it was tuned up recently that may be the problem. And these cars run on Premium 91 octane gas.