Luff, I will confirm the weather statement as well. I have an OS .40 LA that I had never had an issue with. The first really hot/humid day I took it out I had a deadstick on my first flight. There happened to be a real good engine guy at my field that day that saw I was having problems (I am a newbie). He came over, fiddled with the High Speed Needle for about 30 seconds before having it running like a top. If I was you I would get one of the more experienced people at your field to check over your engine. By experienced I mean someone that is good with engines. Someone here made the statement that the guy that is good with engines is the guy flying all day without issue, not the guy spending all day fiddling with engines. In my case the guy that helped me was out there flying nothing but twin engine planes so I expect he knew what he was doing (which he obviously did).

Now having said all of that I don't mean to discredit CG's comments. People have different experiences with different equipment. He obviously had bad experiences with Evo engines so obviously he shouldn't buy them. However if you have had good experiences with them by all means continue to use them. Too many times I see people treat their favorite equipment like a religion. Before you give see if you can't get that engine Exorcised