I'm not a FF driver or owner, but I do own a X-flow powered Caterham which I race. I'm restricted as to the cc class I run in, gasoline octane permitted and piston material which the rules say must be cast. So basically it translates to a FF engine with twin 40 DCOE Webers. I've checked most of the FF rule books and most of them do not permit Mahle pistons. Why? Thanks in advance.