If you think about cars, performance muscle type cars, if running at a drag strip the headers are always in the range of around 40", give or take a few. BUT that same car on the street has to have full length exhaust pipes, mufflers and tail pipes, which of course are a LOT longer.
So some sacrifice is required from optimal to running on the street.
Just my opinion, but I believe the larger pipes will decrease your low end torque and create some peakier and narrower torque ranges. For being street friendly, I think I would error on the smaller diameter pipes versus larger. Again, this is just my opinion on what I've read over many years of being a gearhead.
Likewise with carburetors, if setup correctly, cam, ports, exhaust etc, larger throats will give you higher peak hp, but you will lose throttle response at the lower rpms. Conversely, a slightly smaller carb will improve throttle response but cut down on peak hp. I believe I read someplace back about 20 years when the throttle body injection was coming out and some people were converting old 8-stack mechanical injection to port injection. The 8-stack induction looked cool, but most were of a very large butterfly design. The opinion back then was that as long as the injectors were feeding at the correct amount for your needs, it made little difference as to what size the butterflies were, within reason that is.
I've always thought that the pipes on the M3W were way too long for good performance, but I'm sure that tuning can be done to optimize just about anything.
I'm happy to see some experimenting with the pipes, sounds interesting.
