46th, I'm running a very similar setup, as you kinow. MMM recommends exhaust port inserts for improved flow and outlet inserts to correct peak torque rpm for overly large ID of 1.75" pipes. I'm not arguing the point, but that combination works for me. MMM mentions welding the outlet inserts in place. I drilled and tapped for two 4 mm. screws with countersink heads in each pipe, countersunk the holes so the screw heads sit flush with the pipe, an installed with blue Loctite. Screws can't back out in any event because the mounting flanges of my 17" megaphones cover them. I'm very pleased with the performance.