Been trying to work through some MIL codes and I think I'm finally on the right track.

I've got simultaneous P0171, 0174, 0491 and 0492 codes stored. Indicates running lean in bank 1 and 2 and secondary air flow too low bank 1 and 2. Since I'm getting both banks at the same time I figure I'm looking at a centralized problem. Replaced the secondary air pump, no good. Did the plugs (overdue anyway), coils are good. I have a fuel filter that I need to put in anyway...can't hurt. One day I was just poking around in the engine bay and saw a vacuum line had popped off near the front of the bay, the end was crumbing. So I started replacing lines...and every time I figured I was odne, I found another leak. One audible leak (as in I can hear it over the nose of the engine) is coming from an inch and a half long tube just at the rear of the intake plenum. I'm hoping its my problem, but regardless it needs to be replaced...question is, how the heck do I get at it? I've included a photo here to show the general area above the hose. If you see the hose that disappears below the plastic tray the check valve is on (I've already replaced that too)...that hose goes to a T connector. One long hose goes off and wraps around the motor, replaced that one too...now I jsut need to get the one that dps down inside, but I simply cannot get at it. So if anyone has any suggestions I'm all ears. Does the intake plenum come off easily and cleanly? I figure maybe if I can move it forward an inch or so, or lift it off altogether I can probably get in there and do what I need to. Any other suggestions?

One other thing I've seen is that the lean mix on both banks can also frequently mean a MAF problem. How can I test the MAF to see if its bad? I'd hate to replace it and not have it be actually bad...at $150 its on the expensive side.

Thanks.