Backfiring out of the tail pipe?

I was working on an old mercury marquis, it stopped running on the side of the road, got it up and running and was able to get it home, well when I got it home I popped the hood, and took off the air filter to get to the carburetor, well I started the car (with a little trouble) I got it running at a high rpm (id say about 5k+ no meter to tell) and while it was running I had my friend spray the carb with carb cleaner. It ran fine for a little bit, then started to sputter, I pumped the gas and it continued to sputter, then made a huge backfire out of the tail pipe, before it backfired there was a ton of white smoke coming from the exhaust pipe, then after the backfire all that comes out is black smoke, and it continues to backfire and rumble allot, it has new points, new wire, new plugs, new distributor cap, new ignition coil, new starter, full tank of gas, carb seems to be new, its got a new fuel pump and filter, and is getting plenty of gas, what could have caused to it just misfire that badly that quickly? (And another thing, when I try to start it, even when pumping the gas, it stays the exact same way with the rumbling and backfiring)