Ok i have a weird problem. if i leave my car parked over night or for a couple of hours it will start fine no problem. If i drive and get it to operating temperatures and then shut if off( short trips) and go to start it again it has a very rough idle and will blow black smoke out the tail pipes and missies like crazy. if i let off the gas it will stall. this is only on short trips like if i drive and then shut if off to go into the store and come back out it will start like this. no CEL or anything. what could it be?? this problem only started when it started to get cold. its pretty annoying

i have a K&N FIPK
Skunk 2 70mm throttle body and a header.

 

don't know ...
try the map whack maybe.

 

carbon deposits somewhere?

 

Check temp sensor and also check for leaking injectors

 

Seems like some S2000's have gremlins. Mine would completely shut off while DRIVING, and wouldn't restart unless I let the car sit for a good hour or so.

I basically had to do a complete overhaul of the entire fuel system before my car problems went away.

Black smoke generally means fuel. Maybe it's not the cold (that's just bad timing), but instead your injectors are having probs. Just something you could check anyway.