[jkeyzer]

I pulled the plugs tonight and some cylinders are running much richer than the others despite the correlation being pretty good at idle (I assume it is not above idle). After 300-400 or so miles on these plugs some are white with black smudges and a couple are very black all around (rich, maybe bordering on becoming fouled). What's the best way to fix this?

Should I put all the idle screws at the same spot and adjust the throttle plates themselves to try and even things out (at idle)? Or should I bring the engine up to 3000 rpm and adjust the idle screws or throttle plates to get them the same at that point?

The linkages are adjusted pretty well, and one of the fouled plugs is #5 which should be less susceptable to linkage misadjustment, right?

Also how long does it usually take for a spark plug to show whether you are running too lean or not? Are the white plugs after 400 miles telling me those cylinders are too lean?