I've got an 87 V2500 w/ a 5.7. It's a 8600 GVW truck w/ NA4 code. I'm to the point where I know that with the EGR hooked up, I've got ~21 in. at idle but revving up to 3000RPM and holding will drop to a steady vacuum of 15 in. I then unhooked my EGR solenoid and see that vacuum stays good @ 21...