Did a test on our factory boost guage. I had a pretty nice spare boost guage and i wanted to see how far off our factory mounted guage was off since i had heard from various people that it was off. I T'd off the factory vacume line from the intake manifold and ran the line through the driver window. I noticed right after i started it that our factory guage read 20vac and the other read about 18vac. When taking off at about 10vac on the factory guage the other read about 9 or 8vacume. At 0psi both were very close almost dead even. My alternate guage only went to 20psi but when i made a pull in 2nd gear it read what would have been about 25psi and held around 22-23ish psi. The factory guage read 23psi and held 21psi.

 

Doesn't seem like it's off to badly

 

not really. I have heard people on here talking about it being off so i wanted to see for my self.

not really. I have heard people on here talking about it being off so i wanted to see for my self.

 

It is off by 2-3 psi or about 10%. If you are exceeding 25 psi it will be even further off. 10% is off by quite a bit IMO.

 

Yea thats what i noticed. The higher the boost or vacume climed the further off it was