Boosting while stationary

[Tanker]

So ive got a friends truck (KW T908 w/ cm871 NOT deleted) in our yard that he's sold and is getting picked up Tuesday.. I had the job of making sure it started/was all good to go (its been sitting here a couple of months now). Eventually got it going and noticed that while parked, I can get it to boost to 55-70kpa for a few seconds before it drops back to nothing (thats after revving it to about 1600rpm and holding it there).
I disconnected the egr temp sensor and did the same thing and it only went to about 10-15kpa.
Ill be going in later to do some more work and was just gonna clean out the back pressure sensor/tube and imap sensor before taking it down the road for a drive to see if it does anything. VGT looks fine and can hear it doing its sweep when turning the truck on and off and it atleast sounds like its getting proper travel. No codes logged in roadrelay.

Anything else I should look for?