An 11x6 is too much prop for a bushing .40 engine. It's too much prop for even a strong ball bearing .46 to make its max power. A 10x6 or 10x5 will run a lot better.

Evolution engines are hit and miss. Some guys get them and do fine, while others can never get them to run right. Evolution does have a good reputation for service, so if you get dud you can expect them to fix it. I'm a big fan of Thunder Tiger engines personally. They are cheaper than OS engines and just as reliable.