A desmog will do nothing for performance either good or bad. What it will do is eliminate a lot of potential vacuum leaks. There is a lot of vacuum lines associated with the A.I.R. system & at the age of our Valks they are all suspect. It will also cut down on the deceleration popping that is prevelant with Valks & some exhaust systems.
I have done several & everyone of them had deteriorating rubber parts that were failing or very near failing condition. There is a possibility that leaving the chrome tubes may over time allow exhaust to "back flow" up the tubes.
BTW, I did the full removal on all of them. More work but cleaner.
Pile of parts from a Valkyrie A.I.R. system
