Engine: OS RG non pull start
Pipe: Jammin JP-1 if you prefer acceleration or Jammin JP-2 if you want high-end.
If you have a spare .21 ae mgt engine, you should try to remove the pull/roto start assembly from it, dremel the pin for the oneway away from the crankshaft, put on a rear cover and try that one in the buggy.
What did you do to your wife since she buys you a Mugen? I'm just trying to get some good hints before my own birthday.