Most blm's to 108 - next step advice please

[piperclipper]

1991 GMC k2500 pickup 350 TBI all stock. 236,000 miles. Most blm's head down to 108, but tailpipe doesn't look or smell rich. Runs good only at map's above about 80 - highway uphill for example. Otherwise feels like a miss. Although the ecm thinks it's rich, also recording lot's of knocks, but don't ever hear a ping.
1. Found/Fixed vacuum leak at tbi base.
2. Fuel pressure fine @ 13 at filter.
3. New ignition parts. (ignition module, cap, rotor, wires, plugs).
4. Presently trying premium no alcohol fuel with techron injector cleaner. I might guess dripping injectors if techron makes no difference. (Fuel sprays look like a cone in driveway)

I'm logging on tunerprort assuming $42-1227747

Any helpers on suggested troubleshooting next steps?