Make sure you have enough AFR under load, you don't want it to run lean, otherwise you get detonation (one sign) and burn through the head gasket. That header has bungs for oxygen sensors, but you can always do it old school and check the color of the spark plugs. If it gets a brown color, you're running too lean. Others can comment more fully but check SL6.org and there are plenty of posts/pics on good plug burn color.
