Throttle shaft vacuum leak on new Proform carb!

Carb is 750 Street Series mechanical secondary, pn 67213.
It's less than two years old, but it was sitting drained for 5 months while I had the car apart. Now it whistles at the throttle shaft, and is affecting idle settings.
I think I just need the Teflon ribbons, but unsure which size or thickness to order.
Same problem on a Holley vacuum secondary carb I also own. I would like to order what I need to fix both carbs.
Can someone tell me for sure exactly what parts I need?
Any good tips on the repair process are appreciated as well.

Thanks!