code 12 is a all clear code, the egr is supose to open and close but that is no big deal because the hose from the egr goes to the back of the TBI. vac. leaks need to be check by unhooking the hose from the intake and checking the various hoses, remember the vac. is created from the intake only when running. you might try checking the intake gaskets too.
you've got a tough one
