V3.3 was populated with D100, a protecting 18V zener (between injector flyback rail and GND5) that provides some protection if the user forgets flyback connection (but doesn't use injector PWMing).
However, when PWM-ing (non 100% duty) and powerflyback is applied, if injector-common+ is above 13V, the 18V zener (with very low ampere rating compared to the powerflyback >20A rating) will clamp to GND5 instead towards injector-common through the 5*diode drop powerflyback.
Unfortunately the powerflyback was tested with 12V supply and D100 sneaked attention.
Note: assembled controllers sent out after 2006-jan-11 have these removed.
drawing: D100 diode marked to remove
Customers who ordered assembled controller with powerflyback option and don't want to remove D100 themselves should ask in webshop and we provide a shop on their continent to do so.