The tubes should be in place on all models from 99 through to the time of closure, if not there i have heard that some dealer removed the tubes
why i dont know maybe thinking its the best bet other than ECU damage if missing i would suggest replacing.
I am in the process of adding to this thread the spyhole mod, and the plenum leaf collector with pics as always so they are all in one place on a thread to save new members searching from one post or thread to another.
The first chance i get i will try and get a camera down the plenum chamber with the tube removed and see what lies below
Arctic.