Hi Bruce! Thanks for the compliment. I will do my best to answer your questions;
1. I went with the Magnaflow Dual Exit System (#15460). It is notably louder than stock but not obnoxious at all. It has a mellow deep rumble at idle and at cruising speeds with no drone, but comes alive under WOT.
2. So far, I am averaging about 1 mpg loss in City driving. I was getting 13.5 to 14 mpg with mostly City driving before my mods.
3. I went with the BDS 2.5-inch system. The front uses a 2-piece system that includes the 2-inch strut mount and.5-inch preloaded spacer. The rear uses replacement blocks to lift it enough to keep the rake.