V.Good write-up. I've read more than once on here to replace IC and ICM as a set. Call it scientifical, or just urban legend/old wive's tale, but cost v. confidence tilts me to replacing together. And another ENTIRELY subjective insight = car mags since the '70's have been hawking brightly colored and way more attractive aftermarket ignition parts compared to their oem counterparts. But I collected repeat cases where neighborhood friend's running problems got traced to their aftermarket distributors and ignition coils. While I always weighed in at least a small potential for improper installation or fitment, the excess cost over stock steered me just make sure of good maint. of stock stuff in those areas. What's interesting is for the past near-20 years on this forum I've picked up on numerous cases of the same thing for elec. gremlins, - especially regarding your brand in question and the other popular one. Sure, ACD and Delphi and other 'used-to-be-trusted' reps keep sliding, but for the revs most of us run I've never felt ignition is the weak link on a sbc.
Sorry, just a long way of adding support to your diagnosis and suspicions. And I know you know about the dozens of documented "off-idle miss" issues that just may be contributing to your under power problems.
\'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!