How does this spark plug look like to you?

circlepilot said

My assumption was he had a fuel related question by mentioning "jets." I read spark plugs (aircraft...not a big difference) routinely as apart of my inspection process. Not trying to dispute a timing problem, (aircraft engine timing is "set in stone" by the eng. data plate, i.e. 25 deg. TDC means just that) but his spark plug pictured (in relation to fuel) shows to be a "little" on the lean side, "if" his fuel/air mixture is what is causing his "drivability" issue. Just trying to help.
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The middle plug in this picture is pig fat at idle and rich at a cruise. The plug on the left may be a touch lean but that's hard to see in a picture.

If you have any ignition at all, you will have mostly white porcelain with a .060-.080 wide fuel ring at the bottom. Sometimes, you get stuck running slightly rich (Pontiac for example) because the plug is in such a bad location that when the intake valve opens cold fuel is blown right across the plug making it appear rich.

Reading plugs is tricky. Most guys don't have nearly enough ignition. I'm leaning that way with the OP.