RE: CHECK ENGINE CODES P1411??
Its more than likely a torn or loose vaccum leak going to the combi valves. Check behind your engine and check the little lines going to the valves.
The valves are those big silver things bolted to the back of each cylinder head.
You won't hear a vaccum leak BTW, only when the SAP pump is operated.
It has NOTHING to do with the turbo.
99 Chevy Silverado Z71 6" rough country lift/W 35" tires, 4.10 gears, (4.56 soon) S&B CAI and a flowmaster super 44 exhaust.
"Never argue with a fool, they will lower you to their level and beat you with experience." My personal motto.