Stay away from silly twin piston dump valve, stick with recirc valves. I had a turbosmart recirc with B.O.V. port, worked a treat and gave a nice release instead of the typical ptssh! sound.

When you do fit them, normally you have to reset the ECU for it to relearn. Simply disconnect battery over night, restart in the morning with all the fans switched on, head lights etc. and allow to fast idle for about a minute or so. You may need to do it once or twice, but it will stop stalling afterwards