The engine in the TsT-14 Bonus that belongs to Bob Carlton is more than "slightly different." The TsT-14 for sale has a Rotax piston engine and propeller. Bob's TsT-14 is powered by a PBS TJ-100 jet turbine, which is about as different as you can get without going to a "Mr. Fusion" reactor like on the ""Back to the Future DeLorean.