Anyone know what the small vacuum solenoid next to the turbo pressure gauge sensor is. SE disconnected and plugged one of the connections when they had here recently. Just wondering why?

I think the solenoid you're referring to is the PRVR-solenoid, which controls fuelrail-pressure depending on fuel-temp.

Plugging it is a cheap and dirty trick to increase fuel-pressure.

 

-Eric

Sounds good that I get more fuel pressure, but what is the downside?

The solenoid is used to increase fuelpressure to improve warm starts.

when disconnected it could cause the engine to run (far) too rich on most occasions and it probably causes higher fuel consumption, other then that it doesn't do much damage.

 

-Eric

There are two solenoids piggy backed together in the corner by the turbo guage senser. One is for the EGR valve and one is for the AIV valves. If you have had these items removed (like me) the solenoids serve no purpose anymore.