...cyl. wont fire? it is the two middle on one side and the two outside on the other side, i am pretty sure i have a decent size vacuum leak, if i put my hand over the carb or shut the butterfly almost closed it runs better, i have searched everywhere and tightened everything trying to find a vacuum leak, all the hose are good condition, the carb is tightened to the manifold and its a rebuilt carb i did myself and cleaned very well, new gasket the whole nine, i cant figure out why it is only firing on 4 cyl. plz help, maybe there is something infamous with this motor that i don't know,