6.5 turbo problem
#2
Turbo solenoid. Yes I hear my turbo I have strait pipe on both of mine but you should hear it. Start the truck up and see if you can move the wastegate. If you can it is ether a bad line, turbo solenoid or a bad vacuum pump. I would take the vacuum system off of it and put a mechanical one on it.
#3
if you got a stock exhaust and stock air intake then you wont hear it. check the specs on how much vaccum the vaccum pump is pulling and test it. get a boost gauge and see how much boost your making. 7-9 stock is about right and anything over 12 psi sustained will throw a boost code unless you reflashed your computer
#5