it's hard to explain the sound. the air injection is removed. That was done when the aftermarket pipes were put on. i would say it's just the natural sound of the engine working.

i can't pin-point the noise to a specific part of the motor. or at least haven't had the time to specifically try.

What rpm should we be idleing at?

06 Speedmaster. Black and Sunset Red. SS long slash, 135/45, AI out.