Changing muffler/cis readjustment questions

[LEAKYSEALS951]

Hi there.
I've got a 78 sc that came with a bursch exhaust and a cat bypass pipe.
It's worked pretty well. I like the light weight and (I assume) power.

It sounds okay with the windows down, but now that it's getting cold out, when I close the windows, its got slightly more cabin drone than I want. I've also got an 18 month old riding in the back, and worry about it being too loud. I am also not earning wife points on long road trips.

Call me crazy, but I also like the sound of original exhaust. My favorite was the SSI/ 2 in 1 out sausage muffler on an old 66 I had. I like the high end noises. I'm not trying to make the car a ricer or big block V8

Anyway, I was thinking about buying a used original sausage muffler 1in/1out, and remounting it but keeping the current bursch cat bypass in place.

What I am wondering is...
Is this gonna dog my hp (or is most of the power gain in the absence of Cat)?
Is this gonna make me have to readjust the CIS mixture?

Thoughts? I want this to be a quick simple little project. If not, I'm gonna leave it as is.

Thanks,
Ron

[Reiver]

You may lose a little HP at the top end...if you often drive at 6000 rpm etc....and most do not.
You will probably gain torque at a lower rpm, moving the 'sweet spot' a tad lower than it sits now on your rpm range.
Your car was tuned for the original exhaust system and you will lose nothing at lower/mid range where 90% of a driving takes place...you may even notice a crisper response.
Most folks get a free flow muffler and put it on a stock car thinking it will improve HP/Torque...it will not, it will move the torque band higher (slower response) and make more noise...that's it.
All of the HP gains advertised are only available at or near WOT when the free flowing aspect comes on.....below that, less response.
If you add a freer flow muff to a modified/hot rodded 911 then it may do some good.
Truthfully, the sporty noise makes folks 'feel' like they are going faster......when they are actually the same or more than likely slower.

[LEAKYSEALS951]

Thanks. If I don't need to mess with tuning, I might just do this!
Ron