I thought nominal pressure values were around 165

Yeah, I think that's an older book spec that was never updated, and I've seen that number in my Volvo Green Books as well. However, I've yet to see less than 175 in a healthy B230 (even after carbon cleaning). Also, you must perform a compression test on a warmed-up engine (operating temperature) for the results to be valid. The pistons and rings contract a bit when cold and you'll have lower/inaccurate results.

The next time I compression test an engine that I've not done before, I'll try to get some numbers of before & after carbon cleaning. I do the water sipping method (of steam cleaning) to remove carbon deposits from an engine while it's running.