I too love my YS engine. Superb throttle response, best power in their class. You can usually compare a smaller YS to a larger OS or Saito. the 140dz i have is more powerful than the saito 180. They do like high nitro content, but it isn't required at all.

The learning curve is a little bit steep, and you must make sure you used an approved fuel tank as it will be very pressurized and non approved tanks may split and ruin the airplane. My 140 DZ (and all dzs for that) are fuel pumped so you don't need to pressurize the tank. The dz's also tune differently than the others.

Your Showtime 4d 90 will be a blast with a YS 1.10. You could almost compare the YS to a saito 150. They are just very strong motors, and after running one, i dont think i could bring myself to run anything else for glow.

Let us know what you decide. Hope this helps.