do keep in mind I dont use coil shield, ram air ducts, backfire shield, meta grate on back on air filter, radiator protector and placed coils to create more free air to move through, this significantly amplifies the engine volume. The air ducts removed alone allow allot of "odd" noises to escape from where the tank meets the frame. I really do think the noise is just the gear driven cam timing at work. But again only one way to know for sure, compression test time hahaha