Black smoke is getting worse.
 

Hey guys, I need some mechanic advice. My car seems to be burning out more and more black smoke, I know if it sits for a day or 2 and i start it up a nice puff comes out the exhaust. Im not burning oil like I did before which i guess is a good thing, thanks to putting some lucas oil thickener every oil change for about a year now. But what can I do to stop the black smoke? Basically everytime I punch my car, full throttle or somewhere close to it the black smoke shoots out the exhaust and the cabin area reaks!. Would a engine rebuild fix this? Or is my engine going to do it forever no matter what I try to fix? Should I buy a new engine? I plan on keeping this car for a long time and I want it to run proper. What should I do?

Ok I'm not a mechanic but i would check your spark plugs for damage or build up ?
it might at lest let you know if what's going wrong is affecting one cylinder or all of them
it might help narrow it down

Good Luck

How's your gas mileage?

Gas milaeage isn't like it used be. I also just had a cat back exhaust done and was going to get a header but I figured id wait till I get this problem solved.