Hi Jim, If your 06 has the 3 valve 362HP engine it develops it's max HP at 4750rpm and the rev limiter chip in the computer should activate around 5500 rpm. We have a 2000 with the 310hp v10 which develops it's max HP at 4250 rpm. On rare occasions I've seen my tach jump up to 5500rpm when it downshifts into 1st gear pulling very steep grades, but I instantly back off on the throttle and hold it at around 4000 rpm.
Jim & SherrySeward
2000 Residency 3790 v10 w/tags 5 Star tune & Banks system Suzuki XL7 toad