Misfire at cruise, popping/afterfire at 3000RPM

Coming back to this thread.

Got the heads back from the shop, they did a valve job since all valves were leaking and replaced all springs with new, replaced the rotators with standard retainers. Car ran much better with the heads re-worked, and I also reduced the timing advance from 22 degrees to 14. But I'm still having the misfire/popping. Although it now surfaces around 3400, instead of 2800-3000 RPM.

Some things I've done: new distributor, new engine harness, swapped coils, swapped ECUs, checked timing. One interesting thing I found when checking timing was that I was only getting 10 degrees mechanical advance when I should've been getting 24, according to the literature that came with the distributor.

I plan to change up the spring configuration in the distributor, but there are so many other things going on with the car, that it's time to put her up in the garage for a it. (transmission, steering, suspension...)

The car has a 6 pack, so I went back to double check that the vacuum secondaries were opening. The rear outboard turned out to be sticky, and the front outboard moved nice and freely. I disconnected the rear and performed a test to confirm the front was indeed opening while driving under load -- it indeed is opening.

One other thing I am thinking of, which I will address while the car is laid up in the hospital (shop), is the fuel line from the tank to pump. The car has a 5/16" line, and from what I've read, six pack applications usually call for a 3/8" line. I have a 3/8" line ready to install, along with a 3/8" sender, so that'll get done while she's on the operating table.