I am relatively new and have just in the past year bought a 2000 ex with 7.3pds. It is chipped, intake and exhaust opened and i do have all three gauges on the A pillar. Question i have is that when the truck is cold, say 20 deg F. I start it and warm up then hit the city streets and interstate. This morning on my way to work, I was driving 65-70mph on cruise. The turbo gauge would show 2lbs boost then jump up to 7 lbs without stepping on the gas. I could hear a noise under the hood almost like a throttling of gasses by the turbo when the boost dropped. Is this a problem with my turbo or is it common until everything warms up real good?

By the time i get to work 14 miles away, the truck is warmed up and there are no more issues with the turbo being incosistent?

 

This is the exhaust back pressure valve closing to help aid in warm up. When it closes the boost will drop.

 

Sorry, may have been a stupid question, but I am new to the Diesel engine operation.. Makes sense now!