IF this is a case that the IWEs will not disengage, it could be the IWE solenoid or the vacuum lines to the IWEs. Could also be a problem with the vent lines from the IWE ( the other vacuum line that runs up into the engine compartment, and just hangs there ).
This is the block diagram of the vacuum lines for the IWE ( not actual routing ). You can use a vacuum pump / gauge to see if the lines will hold vacuum. Don't be surprised if the vacuum lines test OK, there is a TSB on the IWE solenoid where it could ingest water, and allow water in the lines, which will not keep the IWE gears disengaged.
Block diagram of the IWE system
TSB on the IWE solenoid ( right click save as )