Aftermarket boost gauge not working


New Member
Hello everyone, my name is Ben and while I have been a member on here I have not been very active. This is my first post. I have an 87 GN. Owned it about a year. It runs idles and shifts really well, however it will knock when going into full boost but thats another problem for another day, until then no full boost for me.

So I purchased an autometer boost only gauge and installed by tying into the vacuum line going from the vacuum block to the map sensor. I am getting no readings at all from the gauge.
My own diagnostics included pulling the vacuum line off at the map sensor and putting some light air through it, from my garage compressor. When doing this the gauge will read and the dial moves. Which leads me to believe no kinks are present on the guage tubing.
Still no reading when driving.
My next diagnostic method was eliminating the map from the question and tying the gauge right to the line coming off the vacuum block with a direct line to the guage no T pipe to the map.
STILL didnt work and I boosted pretty good.
My next diagnostic step was removing the tube from the guage inside the car, it has vacuum at idle and cruise although though its hard to tell on my finger when im trying to drive.
All in all inhave found no vacuum leaks.

The car has had issues running lean.
Scanmaster with power logger
FMIC (I blow couplers from time to time because the gn1 fmic piping doesnt fit well)
Big radiator
LS1 MAF w/ translator
Aero motive fuel pump w/ hotwire kit
TT 5.7 chip with matching 80# injectors.
Adjustable FPR
New transmission from Trans Depot stock stall converter.
Vacuum brakes and new metal vacuum block.
An asortment of upgraded wire harnesses.
Stock turbo set up
New gauge?
Is it a vac/boost combo?

"FMIC (I blow couplers from time to time because the gn1 fmic piping doesnt fit well)". Leaking now?
You have a PL, post the logs, including boost.
Fuel psi is? Log it, too.
ewwweeee big injectors for such a small turbo,,,& stock converter.... hopefully not over kill,,,, yes as Chuck says..... by the way What brand & model gauge is it may I ask? did instructions come with it? what's the fuel psi. sat to at Idle. with reg. line on then off? mind taking a pic under the hood so we can see the connections? maybe something is backwards... Knock can come from wrong settings in the chip too much boost.... chassis movement etc. good you are being safe... yes at idle post all of your scanmaster readings.