So I switched out my boost gauge hose that I had made using IV pressure tubing because I found the piece going around the valve cover getting soft with heat. I used 6 mm silicone vacuum tubing. Now, the tube makes a lot of noise in the cabin - it 'swishes' when it changes from vacuum to boost and makes a tapping noise on occasion. I've made sure there are no leaks by pressurizing and checking. What tube do you use and does it make noise? Is this normal or do I have something amiss? Maybe I should go to copper tubing that I've seen... or maybe I'll just get used to the extra noise, the 'swish' is kinda cool.

 

I found reference to similar problems on other car forums - on a WRX subie forum - guys who used larger boost/vacuum hoses for boost gauges had similar 'noise' problems and turns out some cars have 'resistors' spliced into the lines to reduce noise. The resistors are nothing more than a brass inline connector with a small hole in it. So, it sort of defeats the purpose of a larger line except it may be more durable/longer lasting (not only did my last tube collapse with heat/vacuum but certain areas where it was in contact with metal was being worn away, so the larger dia/thickness tubing should last longer... anyways, problem solved using an inline connector with a smaller dia tube (actually tried a number of small dia tubes but found that a short section of the small dia tube used to hold the ink in a ball point pen) siliconed inside the inline connector to limit air flow...not sure if it slows the boost gauge response much buy using a 'resistor', but hopefully not since it is a closed system and you shouldn't need much 'flow' to change pressures.