Just sold my 97 7.3 for all the reasons your listing.
Payload is very low, 1800-2200 depending on your cab, bed, and drive.
Mine was a supercab, longbed, 4x4 with 4:10 gears.
I had the exhaust replaced from the turbo back to get rid of the flat section, I did not notice a huge improvement.
Tried a cold air intake, made alot of noise but did not notice an improvement.
Adding a tuner made a huge improvement in power and firming the shift points, however as soon as I got in the hills, egts went up fast and had to switch back to stock setting.
The truck needs an intercooler to go with the tuner.
Then you will be able to tow closer to the trucks rating.
Mine was an automatic so the tranny was next to need upgrading.
Also it is the cam position sensor that fails, they issued a recall.
In the end all of the upgrades were going to be more than the truck was worth to me, so I ordered a new one.