The Chapin Poly Foamer Sprayer 3 Gal. (2660E) comes with the nozzle part# 3-4854. The foamer models are listed in parentheses next to the nozzle part numbers on the manual.
The Chapin Poly Foamer would be able to be used with the Boracare and a foaming concentrate to treat the studs and raw wood behind your wall voids. Boracare is the superior chemical to Timbor and will penetrate completely and more effectively, and would be better for foaming applications as well.