Not at all, Bill.
My mechanic told me it had to do with the engine bringing the idle down more gradually when you lift off the gas. This apparently impacts the level of emmisions. My Alfa Romeo 2.0 Spider had a similar valve. All part of the Smog-Nazi agenda, I suppose.
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'81 SC Coupe (aka: "Blue Bomber")
Canada West Region PCA
The Blue Bomber's Website