I have an older model Ford Excursion that has a 7.3 PSD. Recently the MPG had dropped by a couple of miles per gallon, and the power had fallen off slightly. After checking all of the normal stuff and finding nothing, I learned that a leak in the output of the turbo would cause the symptoms. I also learned that the boots\connector tubes on the pipes between the turbo and the cooler were prone to splitting or blowing off of their fittings, and would definitely cause a major loss of mpg and power, and normally a pretty loud hissing noise.

The boots on my turbo did not appear to be leaking and I had no hiss, but one was dirty and oily and that had to come from somewhere. I pulled all of them loose and found that the oily boot had moved enough on it's connector to allow a small leak. Cleaned everything up and put it back togather and solved both the loss of power and MPG.

Hope that helps someone, sometime

Correct!!!
A lot of people over look boost leaks. Not only will you loose power and mpg's, but your also sucking dirty air into the engine and you know that's not good!

Thanks for the advice, I feel like my mpg and a little bit of power has dropped on my 6.0. I'll check it out.

do the ccv mod to the 6.0 and 7.3 to keep the oil out of the boots and prevent them from blowing off.you can clean them real good then spray alittle hair spray on the inside and clamp them down and it will help also. also mpg will go down if you are running winter blend fuel.