on the recirc's you're pretty much stuck with using the pieces that make up the stock venturi. You can bore it out and enlarge the airline fitting (or add new one)...but since these are metric you are stuck with the piece. Be careful not to break it as I don't believe that replacements are available for these.
Does the DDNW150 have the pumps horizontal or vertical? the straight venturi's on pumps mounted horizontily are easier to mod IMO. I have the DNW110...the venturi is an elbow and can be a bit of a pain to mod...but still very doable
