EGR BVSV (bi-metal vacuum switching valve) 

Not only is it a mouthful of letters, it’s an important piece. This BVSV controls the vacuum to the EGR valve (it will not let vacuum flow through unless the coolant is at normal operating temp). 

Hey, we won’t tell anyone you broke off one of the nipples when you were removing the valve or the vacuum lines (or you lost the upper cap). It’ll be our secret. 

OE part

fits 84-95 EFI / CARB (black)

fits 85-88 TURBO and some carb’d (purple)