RE: Thunder Tiger Pro .040
Kevin - I was using the K&B 1L that I bought from Mecoa, but I'm out. Merlin makes one that's about the same heat range, I think it's their 2003 but their website would have more info.
Some of the guys have been using Fireball plugs because they're inexpensive. I'll catch up with a buddy of mine that uses them this weekend and find out which one.
I just bought a handful of the O'Donnell red (hot) plugs and the purple (medium) plugs to experiment with. I prefer a full-length "long" plug over the medium length plugs.
Another one that has been used with some success is the glo-bee style from Merlin. I think they're a cold plug, don't idle worth a darn, but who needs an idle, eh?