FAST reads different boost level than gauge

[TS6]

Dyno'd the car yesterday on low boost, and the felpro says I was at 20 psi, but my gauge says 17- 17.5. I can't find any leaks in my line to the gauge. Its a 3 year old VDO gauge. I do have the 3 bar map sensor, so which one is right? I guess I need to go get another gauge and see, I was just wondering if its possible the FAST could be wrong.

 

[lilthumper]

I would suspect that the old gauge is a lb or 2 off. You have the right idea, borrow another gauge and see what it reads. My gauge vs. FAST reading has always been a lb or 2 off.