SOunds like your truck has problems. The 6.0L has had lots of problem in 2003 and 2004. Ford claims to have the problems under control, but I still see a fair number of problems with the 205 and 2006.
You need to get it to a decent diesel mechanic. If it still under the Ford Power train warranty, let Ford look it over. If it is chipped, remove the chip first.
Ken
KE5DFR
Vintage 1979 Silver Streak Supreme Rocket toted by a 2002 F350, crewcab dually, 7.3L,4.10 axle,SCMT. Travel with two miniature Schnauzers and one African Gray parrot. Practicing for retirement!
I agree there is something wrong, I have a 5.3 Gmc Sierra 3.73 gaser with the loaded 5er probably around 6000 lbs if not more and I made it to shingle springs From Rancho(live) a couple of times and I did not drop below 40-45. the only spot I dropped below 35 was coming out of Lotus from Coloma. I wish I had a Diesel though. I borrowed my in laws diesel to pull to Donner lake and boy was it sweet. I wasnt going to return the truck after that but they insisted.
8PSI??? What were your EGTs? 8 psi and running 5 mph with your foot in they had to be high!
At 2500 RPMS pulling a 7% grade with my 13,400lbs high profile 5th wheel my truck is seing 28 to 30 PSI and running 55 at 2500RPMS. This is with a 2004 F350 SRW.
You have one of the following:
1.) Bad turbo
2.) CAC hose popped off
3.) CAC hose leak
4.) Intercooler leak
Take it to a dealer, preferably one that is good with diesels.