Oh! Let me tell you! At 50psi and it goes off, it lets every one know.
Yes, I used a Tial 50mm, a spool valve from BD, and a voltage switch from Jaycar (P/N 5377 assembled). I did a write up in here some where. I can't remember which thread though.
It has the softest spring you can get (I think it's a 7lb). I had another method pressented to me the other day which is very interesting with less parts (much cheaper if it works). It's not tested to my knowledge though so it will have to go through this process. I'm not at liberty to say yet though (someone elses idea which I hold in confidence). We'll see how it pans out. As you can see. It's mounted as close as possible to the turbo. However anywhere on the pre I/C pipe will do. You will need the aluminum flange to weld it to this. It's a slight pain, but it's been worth its weight in gold for saving the turbos from barking.