The Leo .46 has been used by many people in my club with great success. The only thing I have noticed about this engine is that it comes pretty tight from the factory. It can be hard to start intially but loosens up pretty quickly after the first run. The Megatech engine is the same engine also. I believe it's chrome liner is the cheap replacement for the FX liner if it peels.

I want to bring attention to the Webra 50 GT. This is a very strong and reliable engine. It is priced around the same area as the Irvine 53. These two engines are a cut above the norm
for .46 BB engines. They have more power due to the larger displacement and both have excellent reliablility, but you pay more for that performance too. If you are just looking for a good running .46 then the TT pro, Magnum and Leo/Megatech engines will fit the bill.