Misfire at cruise, popping/afterfire at 3000RPM

One way to insure you are compression stroke. You have a socket/ breaker to fit the front crank bolt? Remove no1 plug stick your finger in and bump engine until you start to feel compression. Now bring timing marks up to TDC. This is no1 on compression "ready to fire. Now mark the wheel just visually you don't have to get "accurate" at every 90*. Now just rotate 90, rotate 90, etc, and go right down the firing order

If you have the valve covers off, you can look at the valves, and feel for compression with your finger same as no1