It really depends, for biology I can sometimes get through a passage+questions in about 4 minutes. Sometimes even shorter for the short passages, and I almost always have about 15-20 minutes left at the end. But for PS it can really vary, I spend more time per question because I tend to make careless mistakes in PS pretty often but I like to do discretes first and then start from the beginning and will typically check the time when I have 3 passages left. Usually I like to have about 30-40 minutes for the last 3 passages. Sometimes I can read a passage and completely blow through the questions, sometimes I don't even need to read it and sometimes I need to read it several times over and note important information. It all depends on the passage type.
I typically finish PS with about 2 minutes left over unless it was a particularly difficult exam (Kaplan FL 4 comes to mind where I ended up not finishing two passages and missed like... 15 questions, yet still got a 12 wtf). At that point I'll just go back to the questions that I've marked. I used to fly through PS but would always make about 5-6 stupid mistakes in the process, when I take my time, I can cut it down to 2-3 typically. Just things like reading questions properly. That is the difference of a point or two for me.