Couple of updates. First, I replaced the filter attached to the side of the air cleaner that the secondary air tube connects to. One side was pretty clean and the side that faces the air cleaner was caked with gunk. Duh, the pipe actually feeds fresh air into the exhaust by a venturi-type effect powered by pulses in the exhaust. So, not as much air was getting into that pipe, likely. This may help.

A much bigger problem was uncovered when I started reading up on how the EGR system actually works. I think I've ruled out the thermo-valve. It should hold a vacuum when the engine is hot, at the port that leads to the EGR valve, and it does. I've verified that the EGR valve holds a vacuum and the plunger moves. The secondary EGR control valve works and the passages are all clear, as when I apply vacuum to the EGR valve with the engine running and pull on the carb-mounted secondary EGR control valve lever, the engine runs rough. BUT, the lever that pushes the other lever, mounted on the throttle shaft is tensioned against the lever that moves the secondary valve by a spring, and that spring is broken, so the linkage doesn't make contact until almost full throttle. It's not supposed to be like that. When I looked at the '86 Raider, I could see the secondary valve move every time I cracked the throttle. The stupid spring isn't obviously replaceable, either. I'll try to think up some way to doctor it so it works again.

No wonder this thing won't pass emissions. At least I don't have to mess with the other stuff now.

John B.