You are correct that the STOCK OEM exhausts are different (Y-pipe to si/so muufler for 04-07, di/so muffler on 08+), however a majority (if not all) aftermarket systems for both the Armada and Titan utilize a better flowing (than the early year stock) y-pipe to si/so or si/do muffler. The seller is correct that his system will fit the entire year range.
2006 Titan CrewCab SE 4x4
Majestic Blue w/ Graphite/Titanium Cloth
Pop Bucket, Off-Road, Big Tow, High Utility Bed
Born: 7/12/06 Adopted: 7/29/06
Mods so far:
Whelen LED Emergency Lighting Pkg, Bedlined S/S Step Bars & Rear Bumper, Truxedo Lo-Profile Bed Cover, 7'6" SnoWay 26 series snowplow, LT295/70/17 Nitto TerraGrapplers, Flowmaster 70 series DI/SO on stock '11 pipes, JBA LT's, Airaid MXP, UpRev, PD'd Grille, Badges & Front Bumper, tinted tails, fog light mod, axle vent mod & more to come!!