Choking at 2500 rpm

[woogy97]

Hello,
My dad has a 2003 early 6.0 liter with the manual transmission. Today, we were accelerating in 4th gear coming up on 2500 rpm coming up on 65 miles per hour ready to shift to overdrive. It kept choking after putting it in OD until my dad took his foot off the gas pedal, black smoke would puff out the tail pipe every time it would choke. It almost sounds like an injector but we have already had bad injectors and know what it's like for them to go. I also know it's not the EGR valve as it is unplugged at the moment. The Rpm's won't drop when this happens. No loss of power, but no acceleration. The injectors should be good, we did all 8 a couple years ago and we redid number 8 injector in November as it went down again. Any solutions would be great. Thanks! This thread will determine if we will be buying a gasser and keeping this as a work truck around the farm and heavy loads and using the gasser as the new daily driver.