95 Burb - Lack of Power

First off - 182,XXX, new plugs, wires, cap rotor, fuel filter. No codes from OBD1 - Sluggish and just seems like air fuel mixture is off? Running (smells) rich and no backfires. Idles fine but under load (hills) just does not want to get up and go! Sounds like it is gasping for air or right fuel mixture. No noises or sucking for vacuum. I do have a single O2 Sensor (3 wire - non heat activated) before converter. Disconnected it and ran, exactly the same sluggish response. Did get code after that but it was 13 - just saying it is disconnected. I do not want to replace numerous items to narrow it down. I.E. Pressure regulator, injectors, O2 Sensor, Fule Pump... I have thought flat cam and read through other posts. I would think Cam would give me some more feedback with misfires and intermittent throttle response or bad idle. Engine is timed and run smooth at idle. I know it is not the tranny, brakes locking or anything like that. Ran great until about three weeks ago, starting smelling richness from exhaust, then two days ago, just starting being very sluggish, Can get it to go but not like it used to. Any others with this situation? Bad gas mileage started same time I started smelling rich exhaust. Thanks all.

New Catalytic Converter and all new exhaust. Improved a power a LOT. Still think there is a miss.