Well, we are not talking binary function, a coat hanger might make it functional too, and I would never state I know more than an engineer, but I can say with a high degree of confidence a sterling conductor in the chain, no matter the variables changes the sound - usually for the better in my experience, and when we might compare this to pieces of copper Appliance Wire (AWM) used in the stock amp, not too far off from Home Depot material, I would bet fairly heavily Mundorf will be a change for the better.
Rhetorical question but why would one install a high end exhaust system in their vintage car to gain a few horse power and enjoy the job, knowing that Ford or Toyota wouldn’t install that level of exhaust quality out of the factory - engineers know there is better, but there is a business decision.
I enjoy doing it, and if the question is, is it all worth it for an estimated 10-15% change or improvement, I’d say yes maybe contrary to many, in my case and opinion, sure.. It’s my mustang.