Trunk Wiring problems of the 2003 Chevrolet Cavalier

"check engine" light keeps coming back on for the same issue, supposedly the "air intake temp sensor, replaced that one and several sensors repeatedly, had the complete wiring harness connections checked and cleaned, even replaced my ecm and bcm [neither of which was cheap], and still has "check engine" light, even after being "cleared" over and over again -- this car was well maintained and the body and sub-frame are severely rotting out left and right -- had a weird leak on the pass. Side front, under the dash. It comes and goes. The car smells like an old sneaker inside. Water would pour out of the passenger side heater duct, but there was no rhyme or reason to it. One I even had soap foam from a drive thru car wash literally come blowing in to the cabin, thru the very same heater duct. Thankfully it has seemingly cleared up, but it is still a head scratcher. I've taken my car to several dealerships, privately owned shops, and even had some "car savvy" friends look her over, as well as my dad [ands ase certified tech], and the check engine light still comes back every time. If I would have known I'd put this much money into a car that literally ready to break apart, I would have saved my money to put towards another car. Live and learn, I guess. She was doing so well for 10 or 11 years and it's like she just started "giving up" on me. She's got 165k on her and the pain has gone to crap, but that's gm for you, kept her garaged, waxed regularly, had her looking showroom new, until recently, the paint's clear coat started to "stipple" [sharp bumps] and bubble all over top panels, starting with the roof, then hood, and now trunk. It's embarrassing to drive her, and I am not paying to repaint her, I already have way too much into a car that likely will not pass inspection coming up in August. I'm now handicap'd and disabled, fixed income, can't afford a new car.