Bought at 06' EVO IX about a month ago. Currently stock. Just added an Autometer Vacumn/Boost Gauge and had questions about what I am was seeing on the short ride I took. I searched and read other posts before this. The car boosts about 18-19PSI and then tapers slighty which is normal based on other posts. At idle I am showing approximately 16hg/in of vacumn which is normal based on other posts I read. However, if I am accelerating and let up on the gas, the gauge shows 20hg/in of vacumn and then holds that if I am "cruising" at 3500rpm in 5th gear? If I start to accelerate, the gauge then starts to show boost. Is this correct? The t-fitting for the boost gauge is on the short hose that goes from a fitting on the front (passenger side) of the intake manifold to a vacumn sensor. Sorry if this is a stupid question and thanks in advance.

 

My IX at idle is usually around 19-20 in/HG, but your car could be different. Depending on the throttle that is being applied will display the appropriate vac/boost level while cruising

 

Yes it's normal. When decelerating my car will go to 20inhg, and sometimes further, depending on what gear I'm in. It's because you aren't applying any more gas, therefore you get no turbo spool at all, and your engine will be sucking in more air, creating more vacuum.

 

its normal, your engine is efficient in different rpm ranges. so naturally your boost/vac will show this as well