the standard dump valve on my 95 wrx has 3 connectors, but i see aftermarket atmospheric ones only have two

which one goes awhere and what do you do with the 3rd one spare?

 

Best option is not to! They tend to cause running problems. But if you do,then you remove the old one,blank the pipe on the intake elbow,plug the dv into the intercooler pipe hose,and plug the vac line to the new dv.Only 2 connections,as the recirc pipe is now vta.

Mit

 

cheers buddy, and thanks for the warning