Sorry Rusty, Without getting Emotive, I'll have to disagree on your last sentence: Going to a smaller tailpipe on most daily OEM drivers can and DOES boost off-idle & low end torque.Period.
The OEM manufacturers, even WITH plently of non-interferance space, wouldn't have built them, without good reason, other than too of a byproduct you mention of quieting exhaust down.
I've had a lot of experience in l6 exhaust systems, both street & race (to the extent of building my own turbo mufflers from muffler manufacturers cases & Caps, before they were ever avail in New Zealand, like my Dad before me, making Glasspacks) & its been proven, in mild/many applications smaller is better.
Also case in point with these Cast Aussie hyperpack clones, I can tell you right now, from past experience before they were a twinkle in casters eye, that 90-95% of the Power increase comes from the SPLITTING of the 2 head pipes & there's a Magic # for the length, quite long for the Pair, 2" is best I learnt in the 70's & on a Dyno you run a pair of 2" pipes under & out the side with a stripe of enamel white house paint run down their lengths: where it stops burning, smoking & really changing color is the best merge point.
About 6'-8' ea depending on the Cam etc. For a 225" 2.25" dia anywhere in its system is more than enough or you loose flow velocity.. Same for the latest flowmaster type drone-boxs - a pair of suitably sized Glasspacks have proved their worth.
Australasia Grew up on hot worked 6's...
Been there, done that since making 2 stroke DG/FMF type 2 stroke expansion chambers as young teen ( cause you couldn't buy em) & hot tube pipes/mufflers for the 4 stroke bikes when a welding torch wasn't too heavy to hold & worn out std too expensive to repl. Etc.
You can run with your Big bores but some know better, all due respect given.
Thanks My friend.