It's not a solid number; it can be anywhere from the late 5's to the early 6's. Apparently, also, mod's can push the redline up a little bit; I think I remember hearing Venom's omgDuratec hitting 6500 or so, and jtzk13's hitting 7k.
My (stockbutold) Duratec regularily hit's 6000; that's also the printed redline on my Tach before the redline was removed. I would put a max at 7 8k and a redline at 6.
I have an 01 SEL and the tach reads to 7000 rpms with no red in any of the numbers......I have had the rpms up to 6500 RPM's several times, it will not go any higher....my only mods are K&N air filter and removed the silencer.
Would like to put a HD-Dynomax super turbo muffler......supposed to keep a stock sound.....but better exhaust flow.