Car isnt running good, PLEASE HELP!!!!

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I bought a 1996 Honda civic a few months back and the car ran really good until I put high octane gas in, not saying that is the problem, but every since then I have run into nothing but problems. I have changed the plugs & wires, took it to a mechanic to get the check engine light to go off (the code was the catalytic converter), was told it was the plugs, put new plugs in, the check engine light would go on & off, so I took back to the same mechanic, who said it was the MAP sensor. He stated that 2 codes came up, the sensor & cat. efficiency. Well, that didnt work , so he changed the fuel filter, that didnt work, he wanted to readjust the timing belt, so I took it to another mechanic who specializes in Hondas, but he stated there was too much work done, i needed to take it back to the original mechanic. I took back to him and said to readjust the timing belt, but if that isnt the case, i am not paying!! Well, it didnt work, and I didnt pay, so now, I took it to the Honda dealer, who says they can diagnose it (of course charge out the wazu), wouldnt you know, it gets there and they can't diagnose w/o the check engine light on, which minds you hasnt come back on in about 1 month........ even though the car wouldnt crank for them and they had to push start it, they cant figure this out! Please help,I have exhausted every opportunity I know and nobody can figure this car out? For real? The car runs OK until the motor warms up and then it literally putt putts down the road. if you stop at a stop sign, it takes forever to get it to go, like it isnt getting gas, then all of a sudden out of nowhere, it takes off. I was told 100 different things it could be, from the cat. converter, to the oxygen sensor, to fuel pump, and the o rings on the injectors...... I was even told the car was a pc of junk and to trash it!!!!