Electronic issue?

My 512 stroker has started cutting off and then catches right back up, ocassionally backfires when doing this and sometimes just quits. It has a 440 source distributor,MSD 6Al box with 8,000 chip and MSD coil. Instaslled additional ground strap. No change. Checked all connections and everything appears to be good. Anyone have a thought on this? Thanks for any help.