My 2002 dodge durango hits 4000 RPMs and bounces between 3000 and 4000 RPMs when I am in park and have the throttle held down. I replaced the cam sensor and it is still doing it.

Chrysler products have a "feature" that sets the rev limiter lower when the vehicle speed sensor (VSS and it also runs the speedometer) is at 0.
This is normal operation. If it will pull to redline when the car is moving who cares if it shuts down at 4k in park or neutral. If you really need to rev it higher in the driveway you'll have to put it on stands and put it in gear.

This is your rev limiter stopping you from over reving engine causing internal damage. this is normal on all new vehicles. Don't know what year they started this but it goes back at least 16 yrs