Backfires when accelerating

I have had several of those cars. Well not specifically the Park Avenue, but GM's with that engine. That is exactly what they do when it is time for new plugs and wires. These cars are very picky about their plugs and wires, so only use the OEM stuff. That is Delco plugs (I *think* single platinum) and any brand of 8mm wires would be good. Any other plug will last for a few months and then foul out. You can save some cash by ordering them online. I get them from Amazon, personally, but RockAuto has good prices too.