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My turbo boost has dropped from around 15 psi to 9psi max. I used to be able to get up to 18 psi in cold weather.
I noticed this in July when I went to Wyoming. I changed my air filter in Wyoming, and that did not help. When I got home I changed my fuel filters. I have not driven the bus until yesterday.The results are still the same. I'm only getting about C24092A3-883E-4021-9F1C-8B32A89B61C8.jpg9 pounds of pressure at full throttle going 65 mph. I'm having somewhat of a struggle just to get up any small hills. I had my turbo charger rebuilt by M&D Diesel in San Antonio for $1345 in 2019. It has about 50,000 miles on it now. It has worked fine up until that trip to Wyoming. I checked for turbo leaks and have found none. I can't see any exhaust leaks around my manifold either. I have no black smoke or any smoke to speak of while driving. I can make a little black smoke with a full throttle kick down taking off from a stop light.
I'm not sure what to do next. Does anyone have any ideas?
Thanks
David

Manifold gaskets blow out or the manifold cracks causes the drop you have a leak some place ,the 6v92 is usually around 20 to 25 lbs. under a good load it doesn't take much of a leak to drop the PSI boost pressure and they can be hard to trace at times, and a worn turbo can cause it very often if one has a small amount of drag on the compressor (hot) side     

If it is a leak, there are a lot of places it could leak. It could be somewhere around the blower because the charged air inlet goes in at the side of the blower.

If there is a manifold leak would I see signs of stains near the escape  point? I would think the  escaping  exhaust would  discolor  the area at the pipe flange where it would be leaking. 

Is there a way to test the turbo charger either on the engine or off of it on a bench? I have to eliminate devices one at a time. 

You can check the turbo on the bus  a little pay up and down you can fell is ok but side movement is not ok,you have to check the manifold on top and bottom not just the upper.If the engine has a throttle delay leaking it will drop the boost too   

I pulled the intake boot off and wiggled the fan. No slop or play. I don't see any issues there.

I can't do a thorough inspection until I go home in 3 weeks.

Would it be possible to force air into the intake tube at the blower and spray soap solution around the six manifold gaskets using something like a leaf blower? 

Quote from: David Anderson on October 21, 2026, 06:32:34 PMI pulled the intake boot off and wiggled the fan. No slop or play. I don't see any issues there.

I can't do a thorough inspection until I go home in 3 weeks.

Would it be possible to force air into the intake tube at the blower and spray soap solution around the six manifold gaskets using something like a leaf blower? 

I use a smoke tester but a leaf blower may work

Ok thanks
David