During my (97) 4.2 rebuild, while plenum was off, I replaced all suspect vacuum hose, elbows..etc that I could. Not sure if 2002 is similiar or not but mine consisted of one 90 degree elbow, & remainder was plastic connectors & short pieces of vacuum hose to PCV except for the long plastic tube going forward to nipple under the throttlebody. Even with that, I found that I still had vacuum leaks in the truck upon reassembly - brake booster nipple had rusted off/holed and further investigation with a vacuum tester of the myriad of multi coloured small plastic vacuum tubes in the truck, I found a cracked plastic joiner in the red line behind the battery box. The above vacuum problems were setting codes PO 305 (misfire detected, cyl 5) and adaptive fuel system lean codes for both banks (PO171, 174). Note that engine vacuum still indicated 19 inches during this time.
I have a picture of the back of the plenum which would simplify explaining but I have no idea how to attach it or post it or whatever to this venue.
Cheers