yes, what I called the IFR for Idle Freed Restriction is the opening to the Idle Well Tube. Which you have reported is at 0.039".

Most, if not all TQ's I have, seem to have a 0.034" IFR stock. At 0.039" I'm guessing your's has been opened up. I'm surprised that with 0.039" opening the idle mixture screws are 4 turns out. However, your IAB changes will effect this. I have never messed with the IAB's. I open the IFR to get the mixture screws 2 turns out. If I over shoot it, then I add a wire.

Cruising is mostly on the IFR, so this circuit is all about the fuel economy. In your case, you may want to try reducing IAB size and see if that results in the idle mixture screws being 2 turns out. Spark plugs should be white if just light throttle cruising, but don't be so lean that coolant temp goes up.

Since my last post, I have had to limit vacuum advance to 16 degrees. And switched to 1950 rods.