Re: 6.8L V10 exhaust and intake...
I had really bad drone on 2-lane highways, when I first put on the Banks PowerPack.
Banks suggested a turned tip instead of straight tip. That fixed it! Still more exhaust noise than stock, but tolerable. Doesn't bother me enough to add any soundproofing. I probably will at some point when I improve insulation and re-do the floor, but not solely for the exhaust.
The AFE intake did add intake noise, but in a good way. It's hard to describe, but under WOT you can tell its a V10 now!
2000 E450 dually V10 wagon