3 months ago my answer to your question would have been "135"

But how useful is knowing everyone's PSI? 300psi on my machine is different from on a porty or small TM. Only if we all used the same machine and tools it'd be a fair comparison wouldn't it? (surely flow rate is the key?)
On my bluewave I generally run a 2-jet wand (total flow '06) at 300-350 for carpets up to 100', crank it up a bit on longer hose runs to compensate for loss of pressure and heat.
With a standard detailer, can't go much above 250 or it gets the walls and ceiling wetter than the upholstery. This is the nice thing about the drimaster tool, because it flows constantly you can use a little higher psi and have oodles of heat pumping through - a hand tool never really gets properly hot because you simply aren't pulling enough solution through to keep heat at the tool.
It's just a shame I've had to send my drimaster back because it sprang a leak after a couple of weeks :
