Thermoquad on 340 (plug photos)

It may be a skosh lean BUT, you have way too much timing on it. I'm assuming pump gas.

I had to look up that plug. Since the ding dongs at NGK can't seem to send me the correct catalog, I did a cross reference to Champion. Supposedly that plug crossed to a 9 Champion but the plug looks hotter than that to me. Hopefully, in a week or so my NGK catalog will be here and it will be easier than using a cross reference.

Ok, so it looks like you have too much total on it, and maybe a bit too much initial.

I'd deal with timing first. You should be able to see a fuel ring down at the bottom of the porcelain where it meets the shell. If you don't have a ring down there, add some main fuel.

The ground wire looks like it's getting a bit hot. It looks like the edges are getting round way too soon for the time/mileage you have on them. Those edges should still be sharp. Again, that says timing.

I'd work the timing first and then double check WOT. You need a fuel ring down there.

I can't see any cement boiling but it is a picture. So I'm not seeing anything that screams smoking lean.

Back the timing off and see what the plugs say. Then sneak back up on the timing.