Yes, and I think a lot of people have been confusing the issue on here recently with their posts. Ok, so with the RevUp engine, they redesigned the lower plenmum/collector with a view to increase top end HP IMO to chase numbers. This meant a loss of torque and also rendered the plenum spacer useless. The MREV2, is a new lower collector - which ironically is pretty much the non-RevUp lower collector - which gives back the low down torque but loses a bit of the high end power - to be expected. The spacer can then be used again to bump the power back up.
So non-RevUp (MY03-05) just needs the spacer
RevUp (MY06) needs MREV2 and spacer to work