Seriously, don't waste your time on that pipe, unless you already own it. Steve is right, that pipe was designed to look good, it is not tuned at all for actual function. An expansion chamber exhaust is designed to to a LOT more then just give back pressure. It is tuned to reflect the exhaust pulses from the motor back at the outgoing exhaust charge with the right timing, the power band of the pipe. The cobra pipe's shape (imagine if it was straightened out) is unlike any other successful moby pipe I have seen, leading me to believe it will not perform well unrestricted.