What do you mean read the stock gauage? Does it have a 3 gauge package under the heater controls? Evo's do not come with a Boost gauge standard. and you would just read the gauge, it should have numbers on the psi side.Take pics and post it so we all are on the right page.
you might peak at 18.5 or 19 psi but it will taper back to 17psi. I thought stock gauge read in PSI? part of the gauge is vaccum on the left side and then once you pass the 0 mark toward the right of the gauge it's the boost side and that is where your PSI or bar will be. You will only hit max when you floor it putting load on the engine. I do not reccomend trying to drive and watch the gauge because it's hard ot see and in a bad spot. Do that at your own risk.
Yea thats right on the PSI at 18 but you have to know to that seeing how its a 2003 it is going to have a plastic BOV that can only hold 14 PSI i think. Thats why stock for stock a EVO IIV well not win to a EVO IX :dsm:
It's in bar, so go Google for "bar to psi calculator." We can't tell you what boost you're running stock - you have to tell us what the boost gauge says.
The stock plastic BOV is only efficient up to 13-14psi, but that doesn't mean the car only runs 13-14psi, and that has almost nothing to do with an VIII vs a IX. The IX has an improved turbo with a larger compressor housing and 10.5 cm^2 hotside, a MIVEC head, revised coolant passages in the head allowing for more boost on the same octane, and it has an improved ECU. The aluminum BOV is a minor difference compared to the above...
I figured out one of the reasons gauge placement is so bad with the mitsubishi 3 gauge pack when I saw them on a British car. In a British car, or JDM car you are sitting on the right hand side of the car as driver, and the boost gauge is then the closest to the driver rather than being the guage farthest away from the driver like it is in our cars where the driver sits on the left hand side of the car.