mufflers?

on the 1776 i run in the car i have always had a big tuck-a-way (hideout) muffler fitted. the big turbo style muffler that bents under the n°1 and 2 cylinder and only the pipe exits from underneat. i always liked this setup because i am not a big fan off the exposed turbo, all shiny, muffler.

it was not supported anymore because the bracket gave way, so i took it off and fitted a very cheap glasspack muffler just to get on the road again asap. But this thing feels so much better. i haven't had the chance to test it all out on the track, but with this muffler a lot off things improved. the sound is less (obvious as it isn't under the car anymore), but also the performance and response of the car is so much better now. it just drives like an automatic in third gear and doesn't bog at low RPMS.
very strange what is happening, but maybe someone can explain. the only thing is that the old one was too clogged up, but i never performed this well on any engine. and i never had oil in the exhaust or something like that.

i am confused about this as the muffler i use now was the cheapest i could get and was meant to fit a stock 1500 engine easily without too much thought or fuss.