If your Defi reads anything other than zero when the car is off then you have either a defective gauge or one damaged in shipping. I did a lot of research on this at Honda-Tech.com before getting mine. There was a bad batch of them in late 03/early 04 and they are also prone to shipping damage. If it's not at zero at rest then it's definitely inaccurate.

 

Do you have a mechanical or electric Autometer? I just compared my Autometer Cobalt series electric boost gauge to a mechanical gauge accurate to within +/-1%. They both agree.

For what it's worth, the mechanical Defi D-series boost gauge I bought a few months back was "off" right out of the box. It read 3 psi. I sentit back. It's too bad because I like the way the D-series look.

 

I have a Omori Multi color boost gauge and it works great. The color adjustment lets me match the dash perfectly.

 

also will depend what you are using for a pressure source. There was a batch of Defi that came in late last year that were off from new by 1-3 psi (read high when in the box). We have probably had 10 shipments come in since then without a single issue

 

I have the Defi D-gauge...looks great..works great...sits at zero when off...it's all good...