Like he said, they're rarely done good. But IF you can pull it off I say go for it. I've seen some cars get a bit of a "stain" on the windshield and roof, but thats about it. I don't think they're any louder than a bumper exit either.
Thats odd. But yes, the Bosch 210s, or 2200s are originally designed for CNG, but in the LS world they are very popular. They work just fine given you tune for them.