benefits of catalytic converter replaced?

[7th gear]

i just had my primary catalytic converter (cc) replaced @ the porsche dealer for free . for those that don't know in ca., there's an emissions warranty on your car for 8 yrs / 80k miles.

when i drove my 986 before it was replaced, i thought i had a smooth ride after my oil was changed. now it's even smoother after the cc change. i sort of miss the 4.5k rpm growl i got w/ the bad one. i still get one but quieter @ about 5.5-6k rpm. the gears seem longer now. when i accelerate, 1st & 2nd gears seem to take me a longer distance on the street compared to before. 3rd & 4th have less engine breaking. i get on the fwy now just in 3rd gear?!? getting into 5th & 6th are now break-neck speed. i can't really push or maxx out 5th gear @ 5k rpms. the car (and myself) really begs for more now. do i need the track now?

this is my 1st car ... ever. so please excuse my green q's i'm wondering what benefits i'll see or you have seen w/ your's being replaced besides less smog??

will my gas mileage improve? at my last calculation, i was @ 25 mpg.
is it better for the engine life?
???

thanks!

[FrayAdjacent]

Well, an old catalytic converter ('cat') could cause flow issues. Backpressure, some people say, helps low end torque... but it could be hindering your engine's ability to breathe well.

Could be that your old cat was not flowing well, which would cause a reduction in horsepower, and a reduction in fuel economy. After all, the engine does have to work to push exhaust through it!