I recently purchased a 1973 Buick Apollo equipped with a Chevy 350 engine and an HEI distributor. The car ran great for me for about 500 miles, then began to run very rough, sputtering and missing when under a load. It would fire right up each time, idle ok, but as soon as I attempted driving it it missed a lot. No backfires through the carb or exhaust.

I noticed the cap was cracked, I replaced the cap/rotor/coil but the problem persists. ALSO there is a 2-wire harness plugged into the cap, no wire is connected in the middle for the ground. Should I run a ground wire from this center pin to the manifold or distributor shaft? Theres also another wire running to the BAT terminal (1 in the harness and 1 by itself), does it need 2 BAT wires?

Thanks!

Josh