1995 912UL miss

The intermittent miss can be tough to solve so assume nothing and check everything from a vacuum leak to plug wires or carb balance issue.

Just a question or two.

You need to try an narrow down whether it is electrical or fuel related. 

What is the mag check and is it reasonably equal? How about checking the carb sync? The gauges may reveal an issue. (Not with an electronic carb sync tool) Re-checked the carb bowls for debris? Some of your comments could point to debris.

When I went thru the carburetors there where really no loose debris. The right side mag check at 3000 rpm drops more than the left and feels like the engine is rougher, if that is a thing? To be honest I have not checked the carb sync. The darn thing idles and runs so smooth I didn't take the time but I can.

Really weird to me why the idling for 5-10 seconds fixes it. I really thought I had water in the fuel somewhere initially.

If it has always been fine before the plug change, could it be a problem with the new plugs? Are any of them loose? Could there be a problem with one of the plug leads? Either the resistive end cap or where it screws into the lead.

When you get the fault can you switch to one ignition and see if that makes it better?

I torqued all of the plugs and double checked them but anything is possible. The fact that it is intermittent is the hard part. We flew over a hour and a half on the way home Saturday with no problems.