Ok, My friend bought my 87 Sundance from me. Heres how it goes......... He blew the head gasket. Got it replaced, Gets it back. Runs Like shit now. He replaced the O2 sensor still runs like crap. Like running pig rich. Today I went over the basics and played with the timing, and got it so it was idling on its own. and my friend revved it up and it shot black soot out the exhaust....And I do mean shot it out. The car runs rich from getting it back, and its almost like a turbo diesel the way it smokes. Anyone have any ideas on what could be wrong???