CARS II,

You should shorten the pipe by about 1/2"-5/8" to get better performance from the engine. The pipe length you stated is too long. Optimum length for that engine is 10"-10-1/8". Cut off the back of the 4" header pipe about 1/2" to get close, then make final adjustments by twisting the tuned pipe itself to achieve the desired length. You may need to relocate the pylon at the rear of the exhaust liner accordingly.

Also, if you'll add 1 oz. of turbine engine oil to each gallon of 15% sport fuel (which is the recommended fuel for this engine), your engine will like it, you'll increase rpm, and the engine will run cooler.

Best regards,
Larry Wolfe
[email protected]