I have a 35 gtr it will some times idle perfect and some times it will idle very rough and wants to die if i dont give it any gas. then if i am idleing around and i hit something hard the motor will start idleing real rough and when i give it gas it will blow a big puff of black smoke. Need some help on what could be my problem?? Thanks for the help

If you have ruled out air leaks in the intake stream (possibility but would probably be more consistently bad if that was it).

Sounds more like intermittent spark. Something to try, when it starts idling rough try pulling a spark plug cap and see if both cylinders are firing (use a gloved hand to do it). If you pull one and it dies then its probably only firing on that cylinder. If you get it rough again and pull the other and it doesn't make an impact then you know which one to concentrate on.

could it possibly have something to do with the float on the carb sticking. b/c a while back i could not get it to start and it was not taking any fuel so i pulled it all the way to gator tail and when i got there hoyt just touched the key and it started right up. he told me that is was probley the float sticking and just by pulling it there that it came loose.