Injector o-rings need to be replaced. I'd be willing to bet you have a few that are burnt/leaking. When you're in there, replace all the glowplugs, and consider replacing the UVCH's (Under ValveCover Harnesses). Now would also be a good time to replace your FPR (Fuel Pressure Regulator) spring, I'm sure it has weakened up some in the 282,000 miles its been in service. Uppipes are also going to be leaking. While it may not be readily apparent, It's a good time to replace them. Get the brass ones that are sold. I Forget the manufacturer off the top of my head, but that will ensure you are once again leak free. Once you get that taken care of, do a thorough service-Fuel filter, trans service, differentials, etc. Change it all. Probably be a good time to check all the hoses for deterioration, especially the MAP (Manifold Absolute Pressure) sensor hose. If it starts to leak, performance will suffer. Remove the EBP (Exhaust Backpressure Sensor), clean all the carbon off of it, and make sure the tube coming from the manifold is clear. You'd be amazed how much performance is lost if that sensor is plugged or restricted.
If you do everything above, I can pretty much guarantee you get all your old power back. Consider replacing the K&N filter with a DIY Tymar setup. Much longer filter replacement/cleaning intervals, and superior cleaning (especially in a diesel!). Ditch the superchip and get a good flip chip (I recommend DP tuner) with a stock, economy, tow, mileage, and performance tune. If you don't already have one, now would be a great time to get an aftermarket exhaust system. Stainless is always my choice, and diamond eye makes a very economical system that fits very well. Ditch the cat if equipped, but keep the muffler. Finally, a shift kit and a 6.0 transmission cooler would be great upgrades for your trans. Cheap, and good insurance. Consider a set of gauges. A lot of guys (myself included) run the insight CTS. Much cheaper than mechanical gauges, and very useful.
After you get all that done, drive her another 300k, and repeat!
2005 Lariat CCSB F-350 SRW
300,000 miles and going strong
12" fabtech lift with 40" Xterrain's on M/T classic locks, Adjustable track bar, Bilstein 7100 reservoir shocks
Edge juice/attitude CTS, SCT with ID tunes, Snow meth. injection, Diamond eye 4" exhaust, 03 turbo, ARP studs, Sinister coolant filter
2010 stone seats/console, pioneer avic d3 with backup camera/bluetooth
Viair 450c compressor, dual 2.5 gallon tanks, air horns rated @115db
Last edited by dazdillenger; 11-20-2011 at 01:53 PM.