P0171 - Fuel Trim System Lean Bank 1
P0174 - Fuel Trim System Lean Bank 2
Vacuum leak maybe.
Yes, press the spring loaded valve all the way in. It should move freely and not stick anywhere along its travel. Clean the shaft as well as the opening, but don't allow carb cleaner to run into the "can" as it can destroy the insulating varnish on the windings.