So I installed the NGR type S in the car earlier (with the single spring mod). The valve wouldn’t open. I just heard the boost backing up behind the valve leaking out when I turned off the ignition.
I’ve now installed the smaller of the two springs. This means the valve will now open at 9 Hg instead of around 15/16 like before. I’ll try it at some point again this weekend. If it works, you can bet there’ll be a video posted. But not until it is working!