Misfire at cruise, popping/afterfire at 3000RPM

AJ, I'm going to copy and save your last write up, since I feel like it may be a while before getting to the timing stage. I think what I'm going to do is 1) repeat LD test with the rockers removed and 2) swap the ECU for a known good one, just to rule it out since it's quick and easy. Then I'll bust out the multimeter to check for continuity where I can.

@MOPAROFFICIAL The air from #4 sounded like it was leaking into the head, but I couldn't pinpoint exactly where. Didn't hear it coming from a valve. Definitely wasn't coming from the exhaust. It's funny you mention the cam possibly being ****, because a couple days ago I told a friend that it'd almost be easier to just pull the engine and rebuild it. At least then I'd know what I was dealing with, but then that would defeat the point of wanting to learn how to troubleshoot.