I have a 1.8 Audi A4. I installed a boost gauge and I'm getting an extremely low vacuum reading. It reads 10 on vacuum. Does anyone have any idea why this might be? What vacuum is usually tapped into for the boost gauge?

 

Manifold vacuum is the best place, like t'ing into the fuel pressure regulator line. You could have a vacuum leak. Could also be a bad gauge. Or you may have tapped a vacuum souce that doesnt provide full vacuum, however if you did this, i would expect the gauge to flutter almost constantly.

 

I tapped into the FPR on my 1.8t and one day i was driving and i dropped to abot 15psi of vac and when i looked at the FPR line it has snapped on one side of the T. So I would definatly suggest like the guy above said to check for leaks.

 

Thanks for the advice guys. It looks like my stock bypass valve is leaking. When I eliminate the bypass valve from the T'ed line I get a vacuum reading of 15 or 16. I'll solve that problem this week when the pipingfor my front mount arrives. I'll eliminate the stock bypass with a blow off valve.