i always read how way off the factory one is,
i just put in a lunar boost guage and its pretty
close to the factory,i didnt have room to open it up
really,but i hit 10 a few times which ive done on the stock
one, when i shut the truck off the guage goes almost to
the top of the box next to the zero? this sound right?

 

I noticed the same thing when I installed my Lunar gauge and pulley at the same time. I posted last week regarding this so you might want to do a search regarding how to zero these gauges under my name. Mine now sits right in the middle of the zero box but I still see 12lbs of boost with a 2lb pulley, 90mm mass flow, cone filter, x pipe in place of stock muffler, and chip. My truck stock would hit 8 - 9 lbs boost, so I know the stock gauge is correct up to 10. Before the pulley it would hit above 10 on the stock gauge with just the other mods. Now I am looking for a 4lb ring for my JDM lower interchangeable pulley setup.

 

yup mine does the ame thing. I have Phantom gauges. My first one was reading 13lbs with a 6lb lower so i sent it back to autometer and within a week i had a brand new one now reading 16lbs in the cold weather with 90mm and intake