340 popping through carb at low RPM.

PRH said
7547 are the leanest rods available.

Make a pretty big change to be sure it’s enough difference to matter.

Something like a 7042.

I am going to have to pick some up tomorrow. All I have is a set of 7347s from another carb. I threw them in for the heck of it and am about to take it for a drive.