THIS MAY NOT BE A PROJECT! This may have become a project due to continuing to drive it. I have no idea yet but hope the best. The CEL is going to tell you what is wrong with it. I do not want to speculate and get your hopes up or dash them to the ground. I have no idea the history or quality of the installs or tune on your vehicle and these can all make a tremendous difference.
The mistake you made wasnt buying the car you now love and want to fix, it was continuing to drive on the modded car when things were not running right. Its okay. You are here now and have not given up on the car at all. Mine has been in pieces more than a few times scratching my head. All fixes are do-able. You sound like a good guy. I am sure someone local can give you a hand or advice in person or refer you to a shop.
It could be something as simple as some bad gasoline and needed a reset of the ECU. This is not going to happen by unplugging the battery. You need a laptop to understand what your car is doing. This is not a honda and is sensitive to mods.
Start by educating yourself about your car and getting that CEL read.
understanding your mods
how to talk to your car