i had a diafram 1 on mine and i lost 10psi of boost about a week ago acording to me gauge, the car felt no slower so i thought me gauge was funked. i replaced me dumpvalve with a twin piston and got me 10psi back. Personally i dont like them but feel i need 1 running 22psi on a t3, when i get me t34 on its going in the bin