That same user (skinnyZ) as linked in the OPs first post, posted this on a 3rd gen F-body forum also, which I believe was the focus (by platform) of his post. Removed were long tube, true dual exhaust headers and supporting system components for '82-'92 F-bodies. These parts were NEVER EPA or CARB compliant, and were always labeled as For Off Road Use Only. These cars never came with true dual exhaust, so it was a configuration that was never emissions certified.

I've seen this topic many places now, but I have yet to see anyone provide documentation that his is the result of NEW rule making from the EPA. It may reflect increased pressure from EPA concerning racing, hence the effort of the last few years to pass the RPM Act (which I too have signed many times, and encouraged others to do so as well).

As far as I can see, there is nothing new here. Emissions certified (CARB approved) headers (shorties with A.I.R. tubes in the 3rd gen. F-bodies case) are still available. Only the non-compliant long tubes for true duals are gone. That's a business choice on the manufacturers part as far as I can tell. Seems to have kicked off with Holley, as part of an overall trimming of their products, including layoffs of staff, which is something a LOT of businesses are doing in preparation for an expected recession.

It would be the same with post-'74 B-bodies. The long tubes I could get for say my '77 Cordoba, were never emissions approved parts as far as I know. Could they be tested and certified? Sure. But that would be a HUGE expense (extensive lab and road testing for each and ever model and engine/trans configuration) for an OLD catalog part #. Is there enough demand to ever justify that expense? No way. So they drop the part.

Has someone seen something more that I have missed (entirely possible)?