So I changed my spark plugs, and the day after the car ran like crap (I'm thinking it's cause I scraped that night after I changed my plugs quite hard). But after that I changed my oil, gas and air filters, which fixed the problem for a day then the problems came back (problems are: CEL, shaking, no low end torque or high end torque, the idle jumps between 250 RPM and 1000 RPM excessively and the car makes a loud rumble noise when I go WOT and it goes no where, it just makes a really loud roar with some choking noises ). I plugged in a tuner and it said plugs 6-8 weren't tight, so I tightened them down, and double checked the other ones, then the problems came back a day later. Someone suggested I check my injectors and my coil packs, which I did, and they were all fine except one injector, which I replaced. Problems went away and came back again a day later. I've replaced all fluids, all filters and pretty much everything I could think of and things that have been suggested, but to no avail. Could it be my catalytic converter being broken after scraping hard? Or is my car on it's last breath?
GT 5 speed manual