Hello, I recently installed a new D.U.I. distributor in my 71 Riviera. Its at about 12 degrees and runs smooth at idle. once I start to drive it it backfires and hesitates like crazy. I tried adjusting the Total timing but my Innova timing light kept going out, it would stay at 2500 rpm for 3 seconds then drop to 1200 rpm then 000 then back to 2500 for 3 seconds. I left it where it sounded smooth at 2500 rpm and drove it and same thing , no power, backfires through carb and pops out exhaust. Any suggestions?