Turbo blow off?

50 psi? something is wrong there.. rather than solicit help from people whom will guess at the issue ( some rather accuratley going by past performance on here ), Take the truck to a workshop and have it ran up on the dyno.
That will show a tech what is happening and allow them repeatability in their troubleshooting.

 

When the boost drops do you get a plume of black smoke out of the exhaust?

I agree a dyno will be best.

 

Yea Dyno best idea! Bu1t if doing this was Vpack on my 2007 Columbia then 2 weeks later Turbo blew

 

So what CAC and what CAC boots are you running on that truck?

 

Pull the air intake off the front of the turbo, grab the shaft and push in and pull out. If there is movement, thats you problem!

 

had that on same engine---its a variable vane turbo--and a controller went-was going ok--then no turbo---so started limping back into london--turbo spooled up a couple times more then died right away---replaced controller at detroit--everything fine
but again--best idea is to take it to a detroit shop

 

This is exactly what I was thinking, wasn't sure though without knowing the year.

 

was on a 06 detroit---and i cant remember what controller the guy changed--he said it was fairly common--it cleared up the no psi problem--but it would still once in awhile-puff and cough when pulling a hill

 

Well it could be a wastegate controller. Or a Delta P sensor (but not likely). Or a boost sensor but again not likely. Diagnosing this problem on the web is kind of hard without having the truck on a computer