My 1999 Saturn SC1 began to run extremely.

My 1999 Saturn SC1 began to run extremely sluggish. I pulled over and looked under the car and saw that the catalytic converter(CC) was red hot. I thought it was clogged so I took it to a muffler shop. I actually ran fine on the way there (because it had sat for a day and cooled off I guess). They put it up on the rack while it was still running. As he was telling there was nothing wrong with the CC because the exhaust was coming out fine, the engine began to bog down at idle. The muffler mechanic told me there probably was a sensor problem judging by the symptoms. He did a code check and it was P0300 and p0340: multiple misfire and no signal from camshaft sensor. Problem is, this particular car doesn't have a camshaft sensor. I checked the coils and they were good. I changed the temperature sensor, throttle position sensor and oxygen sensor. I did this knowing that having issues with these things can cause the fuel delivery system to run rich thus causing fuel to be dumped into the CC and igniting. The car will run fine if it sits overnight. After it warms up, the same problem occurs. Is there anything else that I can check that might cause the engine to run rich?