0.9 bar.
Revo 1 requests different boost levels depending on the 'B' setting. B9 requests 1.35 bar. B0 is stock, B1 - B8 are tiny increments up the maximum.
I run B7, T5, F9 on mine. The differences between the F and B aren't massively noticeable, but the T setting is where the biggest differences are felt. The more the better, but essentially, T4-5 for regular 95, T6-7 for V Power and T8-9 for race fuel/octane booster/Meth etc.
Stage 2 maps request 1.5 bar.
Stage 2+ maps request up to 1.7 bar.
Bear in mind the K04 turbo was designed to push 300hp maximum, which is around 1.4 bar, so anything beyond that is death by a thousand cuts.
On a dyno, my Revo 1 showed 280hp and 330lb/ft some years ago, and it felt pretty much unburstable and consistent at that level of tune. It's probably way less than that now given it's age. The turbo is pretty much done at 166K miles, but it's hanging in there for dear life
Before considering any map, first I would get the car as it is on a dyno as a measure of it's health. A good ED30 knocks out 260hp standard over winter anyway, so for an extra 40hp for stage 1, consider if it's worthwhile for the inevitable lifespan compromise.