The extra fuel seen with muffler pressure may not be from the HS circuit and hence why trimming the HS needle couldn't obtain the leaness obtained without muffler pressuring. It could mean that the LS needed leaned some when on muffler pressure. Keep in mind that electronic ignitions greatly aid idle and it could be that the idle was rich and not detected to be rich.


What we don't know from the observation is if no muffler pressure would have sustained adequate mixture with nose up.