As i drive my 280 Z down the road i can see the faint sight of people keeling over in suffication of the black smoke that lingers out of my tail pipe. I was wondering if this could be a cracked or loose seal, electric choke, or whatever. I also was wondering about the timeing. I know the guy i bought it from wasn't really smart but, the timing is set for 20 degrees instead of 0 and the closer i get to 0 degrees the idle decreases and my whole car begins to shake like its got a bad case of rickets. can some one help me? Please?