AFAIK, the purpose of the bellows is to allow for slight bending for alignment when the bolts are tightened - and to allow for expansion/contraction which occurs from exhaust heat followed by cooling. You'll know if the bellows is necessary if the flange gaskets start to leak. Extreme expansion could lift the upper plenum enough to cause an intake leak at the lower intake/plenum flange joint, but I doubt that will happen. Let us know how it works over time.

Frank

'89 [color:"white"]G-Raider[color:"white"] [color:"black"]Supercharged 3.0L, MegaSquirt 2, lockup A/T, 2.5" exhaust, 172k, Cibie H4s/Oscar SCs, Hella Micro DE fogs, Cobra CB, Superwinch hubs, LSD rear/Aussie Locker front, Bilsteins, Lifeline AGM, Rust-Oleum