Haven't posted regularly in a long time, as my Touring has been pretty reliable. But I noticed a decrease in fuel economy (from ~20 round town to about 17-18), general sluggishness and some pinging on California's 91 octane pseudopremium (I have a D'Sylva chip). I was changing a bunch of coolant hoses last weekend as PM (including that 4-way deal than runs between the expansion tank/thermostat housing/throttle body/heater core- what a PITA) and I noticed that the big black rubber intake elbow itself was split around the connections to both vacuum hoses. The hose from the ICV was also split. So I ordered up a new elbow and ICV hose from BMA and put them in last night. Getting the new hose onto the ICV under the intake was a pain, I ended up having to disconnecting the throttle cables and then moving the throttle body out of the way so I could get my hands in there. I also removed the foreward brace that runs from the lower part of the block to the underside of the intake plenum.
Long story short, the car runs significantly smoother, and feels a lot more responsive. The elbow (13 54 1 726 634) was $28 and the ICV hose (13 41 1 738 187) was $13.
Anyway, this is well worth a check to make sure you don't have an unmetered air leak.