1993 5.0 HO problem with bogging out from 2 grand to 4 grand after that it shoots off like a rocket?

this problem can be related to a weak fuel pump, a coggled injector/s or a weak fuel regulator, have a fuel gauge setup on the outside of the car securly, drive it and see if the fuel pressure drops any under the load and rpms your described, if that checks out, then have your computer read for any codes, i would imagine your check engine light is coming on, if not your bulb could be burt out or its simply not there, either way its fuel related or sensor within that area, the trouble codes will get on target so you not shooting all over to find the problem hope this helps