For some reason I can't edit my posts in this thread anymore... maybe there's a time limit?
Anyway, here are some pictures. This is the vacuum line, starting at the brake booster. The red arrow here points to the first check valve in the vacuum line:
From there the vacuum line is clipped to the back top of the intake plenum behind the throttle body and then loops up again. The red arrows point to each loop of the vacuum line. You can see the check valve in the driver side loop that we looked at in the first picture:
Here is another check valve in the line... getting closer to the IWE solenoid now:
And here is the IWE solenoid. But what's this? Another
check valve? Yep, the tiny red arrow points to it. The T-fitting in the vacuum line that goes to the vacuum reservoir is right next to that check valve but not visible in this photograph. If you look on your truck and move some of the vacuum lines aside, you will see it.
The big yellow arrow above points to the hood on the new style solenoid. If you have the old style, you won't have this hood. Notice the water stains on it already. That's a new valve that I put in a month ago and hasn't seen but a couple rain and snow storms. Water definitely gets up there, which the hood is designed to protect from.
The blue arrow points to my old solenoid, which is not connected to anything. The old metal bracket and the new solenoid hood both include a spot for another solenoid. I just took the old one and moved it over so I would have a spare there if I ever needed it.
The last part of the vacuum system I have a picture of is the vacuum reservoir behind the battery:
A vacuum line (control side) also comes off the solenoid and goes down to a T-fitting, and that then leads to the IWE at each wheel.
Hope that helps.