[Zoom This]

....except that the meter tells me I'm good and the plugs/pipes tell me I'm rich.

Believe in your plugs. They're the closest thing to telling you what's going on inside the combustion chamber.

...jumps like an old two-stroke coming up on the pipe. Does this mean the motor falls flat on its face or comes alive at high rpms? I assume the motor, being undriveable, falls off. As noted earlier, you'll need to stick that tube way up the sidepipe or weld a bung onto the inside of the collectors.