Yeah, they're all governed. The older ones are mechanical, yours is entirely computer governed.
You can get the computer governor removed with a box and get 4000 RPM, but you should have 3200 RPM stock.
BUT, you shouldn't have black smoke stock either. So something's amiss.
__________________
1990 D-250 Regular Cab: Full power screw; stout TC and A518 w/ manual valve body; ratchet shifter; piston LP; Ramcharger tank; manual off; computer-programmable 40 GPH water/meth fumigation; gauges