Re: 04 6.0 Exhaust whistle!!!!
More than likely your hearing a DPPI (MBRP) Turbo Back Exhaust w/o the cat. The 03's are louder than the 04's, but it's a good bet that that is the system your hearing.
FWIW, it sounds awesome at idle, part and full throttle. [img]/ubbthreads/images/graemlins/cool.gif[/img]
Mine: 2003.25 F-350 Lariat CC, SRW,8' bed, 6.0, Torqshift, Toreador Red, Tan Leather, Trailer Tow, Rhino-Liner, Dee-Zee Platinum Box, Adjustable Pedals, Heated Seats, 6 Disk Changer, DVD, 04 Keypad, AIC, 20% Tint, Escort 8500 X-50, Magellan Meridian Color Gps, BFG 285r17 KM2ís. DPPI Dual SS Turbo Back Exhaust,"X" Springs,Issopro EV Pyro,Trans,Boost,Oil Temp, Water Temp, Volt Meter, Air Press., Viair 550C AC, 26" & 29" Hadleys, 2006 Front End, Chrome Tow Hooks, Warn 16.5ti, Billet Cummins Killer Badges, Int. VT-365 Badges.
Diesel_Mom's: (Redhead): Goodbye 2001 EX, Thanks for 4 years. Brand Spanky New 2005 Eddie Bauer Excursion, DVD, Toreador Red</font> , 6.0L Powerstroke, all options including (3) children, (1) 95# Golden Retriever, Goodyear Wrangler 285 MTRs.