1995 Pontiac Bonneville Strange popping noise

It usually makes the popping noise when I accelerate. A co-worker thought it was some bad gas and had me put something to help clean the gas up a bit in the tank before I fueled up. It seems to have helped some as I am able to accelerate a bit faster now, but while I was at a final stop on my way home from some christmas shopping, I got out of the car and noticed a slight smell like maybe burning oil. I popped the hood open and there was some very very light smoke coming from the area behind the engine (The area furthest from where I was standing while at the front of the car). It was a very light grey color smoke. I had the guys at wal-mart look at it since I was there. They were running a bit behind with some tire work but took some time out to look at the car for me. The battery cable was very loose. He says that with as much as it was trying to cut out while I had it just sitting there, he imagined that the popping noise I was hearing was some back firing from it cutting in and out. He suggests I have someone take a closer look at it since he couldn't at the time but imagined I either needed a new battery or a new alternator. I had forgot to mention to him and in my original post that the engine had been replaced within 3 years and so was the battery. I also had neglected to mention that my check engine light was on. There is also a squealing kind of sound coming from the engine area as well, but I've heard it well before this year and it's gone away before, not sure if it might have anything to do with the current problem or not but thought I should add the information in.

Sadly I won't be able to get it to there. I went to pull out of the drive today and it died on me. My dad, who works for a car company and used to do a lot of car work, has looked it over and says he thinks it's shot. I thank you for your time though.