Quick question because I知 not sure if the answer but is the bac valve interchangeable with a t2 and NA. Need this last part for my build and was wondering . I have a 87 gxl that I t2 swapped but I知 missing this part. But I do have a bac for a NA.

 

there are a bunch of different BAC valves for the S4 and they must have slightly different calibrations (passage sizes), but they function the same. the NA and T2 might have things pointed different ways, like the electrical connector, and air hose

 

They all function the same, only difference is you won't have the idle adjustment screw if you're using an NA BAC, if you're on a standalone you'll have nothing to really worry about especially.