We take a standard header and cut to the proper optimum length for the 40. We make a CNC insert to baffler the exhaust and reduce the noise for the least amount of power loss. This is then pressed in with JB weld to help fill and secure the insert. The header is then chucked up to squeeze the header onto the relieved area of the insert locking it in permanently. Header/Muffler can be made with any rise header to suit you planes needs.