Engine Tuning

[Exciter]

I have a Honda Civic 96 LX with about 190000 miles in it right now. At about 3000 miles earlier I have modifications as stock catalytic converter changed to street legal Magnaflow universal type but I made a wrong order where I ordered a single sensor rather than a dual one ( one in inlet and one at the outlet). The mechanic drilled a installed my old O2 sensor at the outlet and my new O2 at the inlet. I also have a new headers and an AEM cold air intake installed. I drove this car after the installation from Arizona to Louisville, Kentucky with a bit heavy load in it for my personal stuffs. After a week I realized I am getting a higher gas mileage and the engine pulls a lot weaker than before the modifications even when the engine seems reeving high. A mechanic from a certain shop showed me that the computer is getting about 30% load even at idle and he thinks the computer is giving more gas as it feels there is a heavy load. He then recommends me to bring it to a performance shop which I did but I was a bit hesitant that the approach might further deteriorate the condition. I am not a mechanic but I heard about resetting the computer by removing both terminals of the battery which I did lately. I realized that the rpm specially at the stop light seems very low like 300 rpm only and the engine then seems to pull a lot better I expect more better after the modification I suppose. Still I don?t know if the computer at that time still reads 30 %. After driving for a day in stop and go traffic and driving around the vicinity where I live, I would realized that the condition is going to back where it was ? pulling weaker again which to seems like the computer is re-setting or I don?t know exactly and so I would removed the baterry cables again in the night time and expect a better performance in the morning. I finally brought it to a shop for tune up here in Louisville but the mechanic does not believe on what I said. Can anybody give me an appropriate advice for this problem and if possible which shop should I bring this car for this kind of problem. Thank you very much for the moderator and to anybody out there who could give me a helpful advice. More power to this forum and helpful mebers.

Exciter