changing the $r(1,$findfile(f:\mp3s\,*.mp3,0)) to $r(1,8000)
give the return of
mIRC 6.16
f:\mp3s\FULLCD~1\KILLBI~1.1(O\14-''T~1.MP3 took 0.109

mIRC 6.17
f:\mp3s\FULLCD~1\VA-LUD~1\05-SHA~1.MP3 took 10.64

so there still seems to big a difference