throttle body spacer
 

05 Silverado 5.3. I installed new throttle body Spacer now i'm running high idle about 1000rpm than goes down to 750rpm with code po174-po171, did anybody else have this problem?

I have same truck an engine, I put a TBS on mine an same thing happened. I drove around about 20 miles, let the computer get used to it, rpm went down to 500, its running great now, but check for vacuum leaks.