Holley running rich at part throttle cruise

Just been doing some experimenting with the 750 HP Holley double on my 408 small block 69 Barracuda after reading the power valve thread. Fitted an afr gauge to check the cruise afr's.

Original setup after dyno was 74/82 jets, 6.5 power valve. Seemed to cruise rich and had a hole in the middle under acceleration but full throttle was fine.

Fitted 72 primary jets and a 10.5 inch power valve. Idle was 13.5:1, light throttle cruise was around 11.8:1, 3000 to 3500 at 60 to 70 mph was 12.4:1.

Fitted 70 primary jets. Light throttle cruise was still 11.8:1, 3000 to 3500 cruise was better at 13.0:1

Im looking at what is causing the rich condition at light hrottle cruise. Car has a 248 at 50 solid magnum cam.

Is it being caused by the idle feed restrictions and do i need to change these to.lean it out a but or is the gauge just reading unburnt fuel.

Once i get this issue sorted i will be drilling the pvcr's to get back to the right full throttle afr and may try one or two sizes smaller on the main jet to get around 13.5:1 to 14:1 cruise afr.

Any suggestions appreciated.