Coming weekend I'll be testing the tach with a resistor in the signal line.
If it works out ok or anything else it would be nice.
Is that an NGK 8mm wire ? It's hard to tell ….
For kicks & being in the Netherlands,, do you have any ''7mm'' Bosch wires to try ?
Might get a better ''accurate'' reading with a 7mm anyway.
''Smaller wire generally has more resistance''.
See that you are a fan of yellow wires like me.
I really like ''Accel'' carbon core, 7mm ''yellow'' silicone wires,, & have made up a ton of them over the years,,, with very good luck.
Not sure if you can get those there or not.
Your build work is extraordinary !!