I have a 78 Cobra with a mildly built 302. We recently put a new ready to run mechanical advance MSD Pro Billet Distributor on it and tried to use a new Holley 770 CFM Street Avenger on it. The carb was too high for it which was making it run too rich. After the previous 650 cfm holley was put back on it the thing still has a back fire. It will idol fine but once it is given some throttle it fires a little from the exhaust. There is also a problem of every time I shift from P or N to D or the latter it stalls out. Kinda stumped. Need some help asap.