Ditto
Long Island, lived my second half of life in Suffolk county.
The exhaust manifolds are the most quiet and heat easy in the engine bay.
Headers release more heat, coated, slightly less. If they’re wrapped, heat is close to exhaust manifolds, but there’s caveats to it. The wrap retains water and will rust out the headers. Companies that coat headers do not recommend wrapping coated headers as it damages the coating.
The style of header and tube size have little to do with heat or noise.
IMO, if quite (inside the car) is your goal, then exhaust manifolds are the way to go and a little grinding on the head won’t hurt and take a little time. Totally worth it.
The muffler is the real big player on inside sound. Not knowing what you have now, I can only suggest as long of a muffler as you can fit and if need be, glass packs before the muffler.
Sound deadening is super helpful as well. That’s another can of worms. EZ, but it takes time to empty the interior and reinstall it after you’re done with the sound deadening material.
I’m not sure how you are about the horse power and it’s potential and probable loss with a quieter muffler, but Walker makes the sound fx muffler that is t very good at releasing hp. But it is quite. Do note they neck down in pipe size once inside the mufflers main body.
