hi mate
from the pic below you can see No.4 (dv) and 5 (washer)
you need both...but...you can try with washer only to see
if it helps as the valves are much more expensive.
some guys reuse old washers some don't
watch for proper torque..it should be 40-50nm but check on that one....
I'm not sure what cause wear of Dv's but best guess is
fuel flow.. bad fuel especially...