Lot of stumbling and hesitation

Grinding noise likely came from the starter drive and flywheel. That in itself can cause a problem as damaged flywheel teeth can cause incorrect signals to the crank position sensor and therefore bad info to the computer.
Some poor running can be attributed to the computer itself as most need to be "flashed" by a dealer to program it to your drivetrain.
I also question the reason for the computer replacement as there are many symptoms that appear to be computer related but in reality are caused by a failed sending unit (sensor), bad connection, broken, grounded or shorted wire or blown fuse that are sometimes missed during diagnosis, resulting in a computer replacement and the same problem that caused you to change it re-surfacing.
I can't tell you what the problem is because to give you that answer would require many hours of actual hands on testing. Chilton has decent wiring and test procedures in their manual. I suggest you buy it if you haven't already. As you "prove out" each system, make notes so you can develop a "picture" of what you found. That often helps bring things together.
By the way...What was the original problem?