Just curious, and thinking out loud here because Im still learning, but if its a small amount of fumes, could it be from the fuel tank venting system. On a stock system the breather is hooked up to the air cleaner, so any fumes etc...would be pulled back into the engine and never noticed right? But if hes running one of the breathers that basically looks like a filter, then the fumes/exhaust is only being noticed because its not being sucked back into the air cleaner?
