There have been a few MDS engines show up at our club and they are usually very quickly replaced with either OS or Thunder Tiger engines. They also do not like much nitro content, either 0% or 5%. Higher than that and they don't like it. If holding the plane up makes the engine quit, it is too lean. Open the needle valve 2 clicks, restart and try it again. There should be no difference in speed when you lift the plane up. If you do decide to replace the engine and go with OS, do not get the LA series! They are a very weak engine. Look at the AX version instead. Also if you check the price differences between the 40 and 46 engines, get the 46. Its only a few bucks more and gives you much more usable power. [8D]