Electric exhaust cut outs

And besides, they are IMO extremely slow. You have to open them before you blast off, And I can't wait that long.
From a dead stop most muscle cars will do zero to sixty in 5ish seconds. If you simultaneously hit the switch and gas, they might be open at 60 and then guess what, every cop in the neighborhood will find you. cuz it takes about 45 minutes for them to close again. Well it seems like it anyway.

There was an outfit in Australia a few years ago that was working on some instant open/close valves, but it never got past prototyping. Which is too bad because at the time, I was hot to get me some.
With those mounted, you could run just enough pipe-size to cruise with, and then when you floor it, POW! the valves open, and the instant you lift, it be like .... "who did that?" That would be like having a spreadbore carb, except on the exhaust side. Me likey