usually black smoke is excess fuel. this is common (especially in turbo vehicles) when one stomps on the accelerator or lets off suddenly. though, in rotaries you usually get a bright blue or orange "cloud" if you know what i mean. it just sounds like your car dumped some excess fuel do to the sudden decelleration, thats all. if it aint broke... dont fix it.





Justin

 

might also be oil burn. a way to test your oil seals is to hold it at about 6k rpm for a little bit, then let off, if smoke comes out then your seals are going. Maybe that's what happened, your sticky accelerator cable performed the oil seal test. Just an idea.