installed a 80 jet in the rear! And same deal after it was warmed up she started backfiring @5200-5500 when she was cold there was no issue.
Although that 80 jet made the engine happier.
So what I have left to do, I ordered a cap and rotor and new plugs and wires. Car needed all that regardless, and a ignition coil swap. I currently have the msd blaster 2 coil with their ballast resister. After all this and it still has the issue going to order Hughes valve springs and 1 of their 5/16 to 3/8 rocker studs (so I can use that valve spring compressor tool) already have there locks and retainers. Let’s see how it goes