Jerry,

Thanks for your help. Unfortunately I couldn't tell much difference in the engine speed when turning the idle ajustment screw. I may need to remove the mixture screw and make sure it is clean (I didn't do that when I re-built the carburetor - I was trying to minimize affecting adjustments - bad idea I guess).

I'm still trying to tweak the carburetor a bit. Currently it's running rich. I THINK (& hope) that I simply didn't ajust the float properly.

Also, I don't know if there is a direct effect, but it seemed to run worse after replacing a leaking exhaust flange gasket just upstream of the catalytic converter. I understand that if it's clogged, the vehicle would run poorly, but it shouldn't cause a rich mixture (I don't think).