The engine runs very strong and has a really neat sound. If you look at the picture you will notice the pressure fitting is located in the larger tubing (1/2") and supplies good pressure for the tank. The larger tubing also gives lets the engine really grunt on the bottom end, it has great throttle response. The first exhaust design was made from smaller tubing and did not let the engine breath and the tank pressure was too much, so I know it was restricting the engine. This set-up works good, I wouldn't say I have increased engine performance, nor hindered it, it just sounds cool.
And yes, the stock header was used along with an 85 degree header extension.