Wow, so many helpful replies so quickly. A bit disappointed that the exhaust cost me so much money and basically wrong.. I did ask for it to be quiet but not hamper the power too much. Just Engines told me that I will loose a little but it sounds like I'm loosing a lot of power.
The model weighs 15lbs and will prop hang on about 2/3rds to 3/4 power, I would have expected at least 1/2 power..
Kevin