Get rid of that plug and throw it just as far as you possibly can! Not in the bottom of your box either.

And as Jester already stated you are too lean across the board.

Be aware old carb settings from before any kind of rebuild or even just a looksee will be useles and you need to start over with both needles.

I too know little about your engine but I did own one for a short while (maybe thirty flights) on one of those Horizon P-51's the so called trainer and after I got rid of needle limiter and the dumb flywheel it dialed in very nicely by tuning to a pinch. It ran so well those flights someone just had to have it and since I never sell but what ya'll got to barter, it was soon gone.

John