Ok, so your carb is the 1406.
Thanks, don't know why I missed that on your initial post. I think that's the one they used to call the emission model, now they call it the fuel economy model. If you've got any tuning parts try a richer jet on the primary side. If you don't, try an experiment, try replace the springs under the pistons that they hang from with something stiffer. or maybe put a piece of nail, or coat hangar under each piston to not let the piston go all the way down at idle, this will effectively richen it at idle and low speed. See if that improves anything and report back.
