Unfortunately, I think that u wil not find a gasser for this plane that will both out perform the Webra AND maintain a reasonable weight for this airframe.

Fortunately , there are many 120 size glow engines that are more powerful than the Webra, Infact the Webra is one of the weaker 120's available and yes , I have owned the Webra, and can tell u that the Thunder Tiger 120 , and Saito 150 (which I have also owned) are far more powerful.

I would also recommend the Moki 1.35 and I am sure that there r others.

I have flown the Cermark pitts with the Saito 150 combo and it is very impressive.

I've also owned a ZDZ 40 and IMO, it is WAY too much power and vibration for the Pitts to take.

Best gasser would be the RCS 1.4 but, only expect the same power out put of your Webra unless you're willing to hang a tuned exhaust under the aircraft.

Sincerely,

Mike