please help charging issue

I have a 1998 Jimmy 4x4 sls. The problem I have is at 2000 rpm the battery light comes on starts dipping bad alt shuts off and it drops from 14.2 to 12.2. After you release the throttle its starts charging again below 1500 rpms. It has done this with a stock alternator and a 190 amp alternator rebuilt alt. Two different batterys two batterys hooked up at once or indivisually. I pulled the duralast battery looking for grounding issues. I found a severed ground off the three factory grounds. I stripped it replised it then the engine warmed up again the same thing. It has one orange wire going to the regulator ared 10 gauge to the battery. Im at a loss what is the next step what would you check next??

Have you made sure the belt isn't slipping at high rpm's? Checked all the battery and alternator wiring and connectors for tightness, cleanliness etc. Sounds like you may have a short somewhere.

I checked belt it is tight I also replaced tension pully. I have to check connections to grounds on the engine front end do to corrosion but battery and alt connections are fine

I replace fusible link below the battery tray still doing it. I checked the orange wire going to the regulator on the alt once I hit 2-3000 rpms it shuts off rgulator voltage and cuts alt out so I'm pretty sure its not the alt or the battery.

This is what is happening now I rammed a test wire in the regulator wire to measure voltage. When car is running I'm seeing 12.2 volts dc at regulator rev engine to 4 to 5000 rms regulator voltage drops to 1.3. I unhooked regulator turned it back on I'm seeing 11.3 with no alt running rev the engine to 5000 rpm voltage drops from 11.3 to 10.9. So plug it back in to the alt tourn it back on 12.2 rev it up 1.3 and alternator is real hot but rest of the engine is not that hot. I think it is the alt.

Sounds like you may have found the problem, that's good detective work.