Rich Fuel Mixture but no codes on 1995 Cadillac Seville SLS

I have been dealing with this major issue for some timenow. The car started burning alot more gas and initially I cleaned the throttle bore. Since, I have replaced plugs (AC?Delco), plug wires, throttle position sensor, fuel filter (very dirty)and the engine coolant temperature sensor. At one point, the catalytic converter got so hot (clogged) that it melted the carpet under the gear shift console. I had the cat. cut out (there was no 'after-cat' sensor so we "assumed" this would be okay. At least it was better than the car burning up. I intend on putting another in when I can more easily afford to. I understand from research though that a bad fuel mix is most likely what caused the caat to clog. Is this correct. Also, on the throttle position sensor, I saw on a forum that I can't find again where the procedures were described on how to reset all f the components on the throttle assembly (throttle pos. sensor, idle air, vacuum solenoid (is that what it's called?...the plunger thingy :). Can anyone help me with those? Also, I know how to take snapshot, get the pcm data, inputs, outputs, et cetrera but can anyone point me in the right direction on how to diagnose the se type problems using them? I know I should and should 'have' paid for a shop to put it on the big computer but I am trying to learn as much as I can abotu the car as I hope to restore it and have it around for a long time. It is a beautiful and timeless model...Monochromatic Black with Black canvas top (faux convertible) and dark tint. I would be overwhelmingly appreciative for any and all help you guys can give. (Oh yes , I went out and bought a digital voltmeter, so I am "armed and ready.") THANKS IN ADVANCE.

You may try changing your O2 sensor out. This could be the cause of all your problems with the dirty injectors and catalytic converter.