Flowmaster requires you to trim the oversize head pipes to the proper length to fit your car. First, make damn sure the rest of the system is exactly where you want it. Bolt the reducers to the header collectors and slip the back of one head pipe into the H-pipe assembly. Raise the head pipe, as shown, and mark where you want it cut so itll slip over the reducer cone. Remember, the pipe swings in an arc, so youll want to cut the pipe a little longer than whats shown in this picture.