I didn’t like the high curb idle 750 rpm (in gear) causing the rear differential clunk & the engine still died. The stepper motor pins were stuck in rich giving that constant deep throat pitch. I put in a new EGR valve (wouldn’t compress), oxygen sensor (it was there) & took apart & cleaned the stepper motor. The pins loosened up. I’ve got the curb idle down to 550. The pins actually moved to rich when I leaned-in the carb screws but deep throat is gone. When the fast idle is on now, the pins move but the last time they will move is when the fast idle releases. Its running nice & hasn’t died but I don’t like the fact that those pins never move in neutral if I throttle-up the engine. Upstream & Downstream are on the bench but both Tower ports are plugged. I notice I have a head gasket leak of oil noticeable in front at the first exhaust port area. There is probably a slight compression loss but can affect this problem? I’m close but still missing something.