thought I would share and if it may be of use to any others. Basically, mechanical boost gauges (non liquid ones) seem to suffer from booost gauge needle vibration. The small pressure changes in the system create noise and this causes the needle to bounce around. When boosting, the needle will often shake violently making it hard to get an accurate reading. The needle will also buzz as the needle shakes.
Some mechanical boost gauge kits like HKS come with an in-line filter to get rid of such noise in the boost gauge line. Some people report that using a small fuel line filter gets rid of the buzz and noise as well, while others say that it makes little difference.
I purchased a small air regulator valve from the local pet store. You can pick these up for like $1 but I could only find them being sold in a small kit, so ended up purchasing this for $7 with some other pipes and stuff. I do actually have pet frogs so figured it may come in handy to have some spare pipes anyway. The air regulator is green and is adjustable. I first attached it to the gauge using some spare 4mm line (see picture). Starting with the valve open, I drove the car around and everytime I saw the gauge needle vibrate, I would tighten the valve up half a turn. I kept doing this until the vibration and buzz stopped.
Now the gauge operates perfectly, and the needle moves smoothly. I used some spray on adhersive (although you could use some silicon) to make sure the valve wouldnt come unstuck and tucked the valve in behind the dash out of view.
Hope it helps someone,
William
