What is the false-positive rate for an HIV PCR test and when, after exposure, can it be taken?

I hate when the Google fails me and provides me with all kinds of useless websites that don’t make sense on a topic. My friend had a possible exposure to HIV about 2 weeks ago and is in panic mode right now obviously. The HIV Eliza test is far away and he’s considering the HIV PCR test which tests for HIV earlier on. However, everywhere I’m looking, I’m getting contradictory messages. Some sources state to take the test at or after 28 days from exposure, others say to take it within 3 weeks from exposure. Then some say it has a higher false-negative rate whereas others say it has a 3%-10% false-positive rate (which is pretty high, imo). Anyway, I was wondering if anyone has had experience with PCR tests (he might also consider the P24 test as well) and if you can locate better sources that out there or have some at your disposal. Thank you.