'77 280z running rich at idle, AFM screw doesn't work?

Hello everyone, maybe somebody can help me? My 1977 280z is running rich at idle and the idle mixture on the AFM doesn't seem to help.

I spend the last few days cleaning the electrical connections and timing the ignition again as it was out of spec. The car runs way better but the AFR gauge I temporarily installed still shows 11,5 at idle. I'd like to bring that down (or up depending how you look at it) to 14,7 as the car stinks of gasoline. The previous owner mentioned that the car running rich was the reason it didn't pass inspection (auction company didn't mention it had no valid inspection on it, APK over here in the Netherlands).

After cleaning all the connections and checking the timing I tried messing with the idle air mixture screw but that didn't help. When turning clockwise a bunch the car did start to run richer at some point but when turning anti clockwise it didn't get past 11,5 AFR.

Can anybody help me diagnose the problem? I would really like to drive the car on the road before the winter stop (oldtimer insurance). Also still waiting on some parts from Zservices EU but some are on backorder.

In my quest to make the car run as it should I did notice the ignition coil is a 1,5 ohm unit with a total resistance of 2 ohm with the external resistor. I believe it needs to be closer to 1 ohm total so I'll probably replace the coil with a 0,5 Ohm one. Can somebody confirm this?