Birdstheword

88 lo3 , i did an upper engine rebuild after a blown head gasket " new seals on valves " , after putting it back together it ran rich , so i brought it home and tried to find out what it was , later i found out that my drivers side exhaust manifold was loose and so i tightened it and that fixed the problem for a little bit , the problem came back as soon as i set my timing to 0* TDC , ever since then i cant get the white smoke to go away , i was getting a couple of codes " one wich was a coolant temp sensor " so i replaced it and now i have no codes , and still runs rich , i have gone through 2 oxygen sensor because of the rich condition , i dont know what else to do , im not an expert mechanic but i am willing to give it a try , what else could it be , i have no SES light and it runs like crap , i even tried advancing the timing " since im running 91 octane" and it ran worse , what else could it be ? could some sensor have got messed up after running so rich for so long , any suggestions?