1991 1500 goldwing popping during deceleration

[apexxx6789]

1991 Goldwing with 17k, purchased last year.
-Popping noise when letting off the throttle.
-At times idle is not stable in nuetral / different than in gear.
-During troubleshooting found covering the vacuum line on the top right of airbox during decel resolved issue.
-Anyone have any tips on troubleshooting down to component level? IASA valve? pair valve?

[Crusty1]

The service manual has good testing procedures for the pair and air shot systems. Vacuum leaks at rotten hoses that operate those systems are common causes of the popping.