As MWfire tried to explane, on PWM, AVR output to that mosfet is in high-Z state.. So, mosfet driver will see 62500Hz from OC0 output over that resistor (witch is 2K2 on v3.4)...
On ramp up time, AVR outputs low state to mosfet driver and override PWM...
On injector off time, AVR outputs high state to mosfet driver and also override PWM...
In this configuration, I use one bank for high-Z gasoline injectors (INJA-INJD), and another bank for low-Z LPG injectors on PWM (INJE-INJH)...