I recently changed distributors and have had all kinds of problems since. The car ran good right after the change, but next day would hardly run at all. I checked the distributor and made sure that timing is right and that I don't have any crossed wires. I decided that it was fuel related. I rebuilt the carb and finally have gotten an acceptable idle back in it. The problem now is that from about 2200 rpm up, it starts backfiring. I've got an air/fuel ratio meter and both banks go full lean. If you fit the gas hard, it smoothes out and the mixture goes back to normal and then back lean again. I suppose that's the accelerator pump kicking it back up. I've checked for vacuum leaks and don't find any. The plugs, wires and fuel filter are good. I even went as far as to check for broke valve springs and rocker settings. Any other ideas?

The new distributor is a Crane Fireball optical trigger and lx92 coil. I'm also using a Crane Hi-6 cd box that was already on the car and was used with the HEI that I've replaced. The carb is a Holley 650dp on a Performer intake.