Bxclip,
Stick with the thundertiger, with a little modifications, they can be made to go quite well! Near as well as most race engines. Unless it's worn out then I say get any good Italian rear exhaust race engine with a turbo plug and buy yourself a start box. More key though in my opinion is what pipe you use in conjunction with what engine. There are good combo's and bad ones. I personally stay away from pullstart engines, only for the reason that I'm scared the pullstart will fail right before a main event or something like that.

BK