When I've used it on the Sprinter I've always pulled the intercooler pipe off & directly into the manifold.
Note that it is advised on the tin's label to squirt it in whilst the engine is being cranked - probably to stop the glow plugs igniting it!
It will be ok to spray whilst engine running
 
I assume so!
My engine's always fired & run whilst I've still been spraying.
Or just try crank & spray & stop when it starts to begin with.
 

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