Your symptoms do not sound exactly like I had, but enough same components at play that you might pick pieces/hints from here:
If you have true climate control then it's called a module. A used one is a viable gambit, but did not pan out for me. I found cheaper equally performing alternates to "that genuine GM feeling".
EDIT: As referred below, parts procured on this forum are historically more reliable than internet, though I (luckily) got extra-rapid refund for my (unfortunately dead) ebay purchase.
\'96SS SOB: SSRI, Herter Tune, Tri-Y II, , 3000 Edge, F/HO bars, METCO extendeds with CV MMC, Bilsteins, currently Vredestein Ultrac Sessanta (315/35 rear). Finally, wait for it... LT-4 knock module!
\'96FWB BUW-Butt Ugly White: PCMPerformance tune, HDFA w/ swissed filter, 1/2 SLP s.s. catback with H- and Flow Super 50s, oem opti rebuilt 3 times, SS Bars, METCO LCA, Airlift 1000, Monroe SS, PowerTrax No-Slip, CTS wheels with +1 rubber. Finally, yes again... LT-4 knock module!
Last edited by 96 Black; 01-14-2019 at 09:33 PM.
Reason: possesive case v. contraction don't cha no- Plus editorial on forum sellers