Boost gauge accuracy/vacuum signal question (pictures)

[red240ne]

I'm having trouble with my boost gauge reading -15psi on vacuum and 3-4 psi under boost. My T28 actuator is supposed to be around 9psi. I've checked everywhere 100 times for boost leaks, and I'm pretty sure I've narrowed my problem down to just the boost gauge giving an inaccurate reading. Also, just for reference, I have my EGR system removed as well, with the EGR port tightly sealed.

Also, I know I'm under boost when the boost gauge is reading around -4psi, because I can feel it... and it will peak at about 3-4psi, so I'm just stumped right now. Is my boost gauge bunk? I've never had this kind of problem before...just looking for some other opinions..

anyways, here are some pictures of where I'm getting my boost signal.

One end of the vacuum line comes from the back of the manifold, circled in yellow

here is where the other end of the line goes

[WDRacing]

Use the FPR vac line. There's a reason everyone uses that line, it's reliable. It's also important to use the same source for the wastegate and the gauge or you'll see different boost levels.

WD

[red240ne]

yea that's what I used on my last setup, I just thought this would be a decent source since it came directly from the manifold, but I guess not. And I have my wastegate/BOV tee'd from the brake booster line BTW, but maybe I should do that. I think I'm just gonna get one of those vacuum blocks from JGS...

[red240ne]

I've really never felt comfortable with double tee'ing the FPR though...but we'll see

[Florida240sx]

Why not. Countless people have done it. If your afraid of it popping off and then goign lean the chances are the same if you have it T'd or not. If you are T'd off it then your boost gauge will show something has happened. When I am boosting I pay more attention to my boost gauge than anything else. Rpm I can here sound based, and wideband is next to boost gauge.

[480sx]

Have you made sure your vac line is free of obstructions/holes? You can buy a cheap boost gage for like 20 bucks from autozone that will help you isolate your problem.

From your description it sounds like your gage is bad.

[red240ne]

yea i'm honestly starting to think that my boost gauge might be bad...i'm gonna swap with someone tonight to isolate the problem

[red240ne]

so i swapped out with a friend and got the same results...Apparently I have a boost leak but I have NO CLUE where it would be. I still think it would be an obvious boost leak if I was losing 7psi of boost. Maybe my wastegate actuator is stuck...gonna try pulling the wastegate signal off to see if it boosts higher than 2 psi.