We've put about 30 hours on our plane since it's annual at the end of July
at which time we noted our plugs were pretty bad and most of the electrodes
were no longer very round, so we knew it soon would be time for new plugs.
Shortly after, our crop dusting friends called with a deal on new iridium
plugs, 1/2 price... $32 each. I've got them in the left engine but have
been waiting for an excuse to put them in the right engine. Now I've got
it, a re occurring fouled plug on the right engine. Like yours, it cleans
up in flight, but re-fouls occasionally on the ground, even with very
aggressive leaning. So, this weekend the right engine plugs will get
changed.

Jim