How do I identify the intake & exhaust valves on a Mazda 6 Diesel

Hello,

I'm having trouble telling the difference between the intake & exhaust valves on a mazda 6 [RF7J] turbo diesel engine. I've searched online and looked in the service manual but can't find any refrence to which is which, most sources say that generally the intake valves are on the intake side etc, but that doesn't seem to apply to this engine as the valves are on the same side.
Any help would be greatly appreciated !

Thanks,
Marlo