Mark I have been running a shimmed WG spring for years. I pull max of 20psi on my VDO. I do have an IA stage 3 chip, and a k24/26 turbo from 2B. Car has over 200k miles and pulls like a freight train. When I hit 22 or 23 psi, I get the fuel shutoff, so 20 is max on my setup. Regards, Jerry '91 200tqa