I just re-read your post and noticed that you put a '93 motor in an '84. Are you using the exhaust down pipe from the '93 or the '84 ? The '84 has a "double tube" down pipe and the EFI trucks have a "single tube" . When my manifold was glowing I had the "double tube" down pipe from an early model on it because the "single tube" cracked. I had the bung for the O2 sensor welded in the "Y" where the two pipes meet. This is now one of my suspects as to why mine was glowing. When I first noticed it glowing I tried it with just the open down pipe and no exhaust and the manifold would still glow, so I didn't think I had any restriction in the exhaust and was looking for a problem somewhere else. But when I put the '93 EFI on it I also put the single tube down pipe from the '93 on it and now it's fine. I'm not 100% sure that the down pipe had anything to do with it, but if you have the '84 downpipe I would get one from an EFI truck.
