Q: Oxygen sensor problem

I cleaned my throttle body saturday 18 after I send my car to the shop to replace my breaks and the disks, I bought a throttle body cleaner so followed the instructions everything was alright the same afternoon my car wasn;t shaking so much like before, that day and the day after was good,so monday I send it to the shop again because the cat converter was all messed up so I bought some aftermarket headers my mechanic put them on and was good the first couple of our but then it started to get loud so I thought that maybe was alright which I realize now it was, after that I got home turn off the car but before that I check if everything was alright with my engine I pooped the hood and my engine was shaking thing that I've never seen since I bought it but I saw that kind of shaking when you disconnect the baterie and I thought it was alright so turn off the car but at the time I wanted to locked the doors i couldn't ny baterie was disconnected so after that Im getting low rpms

My car has 137000 miles.
My car has a manual transmission.