There are aftermarket throttles available though...for the .010 .020 .049 .051 .09, and .15 Cox engines.
They wrap around the exhaust ports of the sleeve...( a variable restriction of the exhaust )
There are also carbs available for the TD .049/.051
Take a look here:
http://www.rcuniverse.com/forum/forumid_70/tt.htm
There's a whole forum devoted to the small stuff
