It should quiet it down, I love the looks of the tail pipes under the cobra bumper, ahhhhh, with some nice 3 inch stainless tips, or Ive even seen some nice 3 1/2 stainless tips. Its not going to to be omg difference or anything, should sound nice
I'm not so sure tailpipes make the sound QUIETER, per se, but they make the sound more DIRECTIONAL, and they take a lot of the bass away from the tone. That was something I noticed immediately with mine when I've played with side-exits, tails, and dumps over the past year or so. With dumps, the sound just resonates from under the car in all directions in general, and the underside of the chassis sort of acts as a baffle (think of it as a big speaker box) so you've got all this nice-sounding bass, and the sound goes out in all directions ... including straight into the interior. On mine, especially with an off-road X and Violator muffs, it's WAY loud if you stand directly behind the car, but if you're standing beside it, it's pretty civil, and likewise if you're inside.
Bigger diameter tailpipes (like 3") will give bigger bass to an extent, but getting too large (like ricer coffee cans) just makes it sound gross.
the only reason the dumps make it louder is because the sound waves bounce off the undercarrage and make a loud racket the tails have an open atmosphere to blow the exhaust out so it it quieter, ive had both tails and non tails, I had tails on the 86 when I bought it and tails on the 7up, now I dont have tails on the 86 and it sounds much meaner, but dont think about carring on a conversation with anyone or listening to the radio.
It's been my experience that it does seem to quiet down some exhaust, while on others it just directs the loudness towards the rear of the car. In most cases it's going to seem like it's quieter, although that's just because the sound isn't directly under the driver anymore and is behind the car. As for how it sounds, in most cases you're going to get a less rumbly/bassy sound even if it still is rumbly and deep with the tail pipes (i guess you need to have ran both dumps and tailpipes to understand).
I think straight through race style mufflers sound better with tail pipes, while chambered mufflers *sometimes* sound better dumped. I will say this though...i've never heard a muffler that sounded worse WITH tail pipes, but i've heard a lot that sound like total crap dumped.