50hp shot, do you run like two nozzles, (one per carb plenum) or four (one per cyl)?
I'm slowly fitting nitrous to my supercharged A15. My set up is drawthrough, and I have my nozzle mounted in through the side of the plate which adapts the carb to the supercharger.
What 1/4 mile times has your car run thus far?
What fuel pump do you run to supply your nitrous system? Remember when your manifold is on boost, that fuel supply to the nozzle will have to overcome the boost pressure, potentially reducing the amount of fuel delivered and creating the risk of a dreaded lean out. Not trying to sound preachy, (it looks like you know what you're doing) just offering some advise.
Is your blower an eaton, or some variety of screw blower?


BTW, Your car is everything I love in a 1200. A two door seedan, (DROOL) and a force fed A series on the bottle. It couldn't get much better!