If you don't have a good dial/knob dampener for those pressure guages (I've never found any of the dial type gauge things to work too well, IMHO) what you can do is something that we use to dampen the response in other manometers, rotameters, or any pressure/vacuum devices, really. If you can get another bit of hose the same I.D. as the hose that connects to your pressure gauge, and another piece of stiff tubing that has an O.D. that matches the I.D. of your other tube/hose, but which has a much smaller I.D. Then:
Cut a 5-6" long piece of the tubing that has the same I.D. as your pressure gauge tubing. Cut a 1/2" to 3/4" long piece of the smaller, stiff tubing. Push the small piece of tubing halfway into the pressure gauge hose and then push the other end of the small tube into the 6" long piece of new larger tubing. You then hookup the larger, added
hose to the vacuum port of the carb.
The restriction imposed by the small diameter insert acts as a pressure "dampener" to slow down the response of the needle. But it won't change the measurement value itself. You can experiment with different I.D of the inserted tubes and/or different lengths of it
for more or less dampening (longer and/or smaller I.D = more dampening). It works best for the inserted short tubes to have MUCH smaller I.D. e.g. if the other hoses/tubes have an I.D of about 5mm you'd want the inserted short tube piece to have an I.D. of less than 1mm, if you can find it - otherwise you'll need to compensate with much longer piece.
