I am not sure if mrublaster will clean prefetch. But if you want to clean it or even disable prefetch you can find (Prefetch clean and control) at the link. I have used it over a year with no problems. http://www.majorgeeks.com/download2495.html
a prefetcher cleaner plugin would be cool to have more MRU Blaster. But 1 thing I've heard, the prefetcher helps speed up your system a bit or something, by putting common used programs into a "cache" sort of area. And the prefetcher directory should only be cleaned once a month or so. So, if a prefetcher cleaner plugin is added, give an option for a variable of days of when to clean that particular directory out I know a link was given to a prefetcher killer, but it would be cool to have all of these options under 1 roof so to speak hehe.