If you search for R3000 you get "The following words in your search query were ignored because they are too common words: r3000.
You must specify at least one word to search for. Each word must consist of at least 3 characters and must not contain more than 14 characters excluding wildcards."
Same for P600 or P800.
I know phpBB is fairly bogus for searching (or at least was a few years ago) but is there maybe a way for you to tweak some settings to allow for these searches here?