Codes P2191 and P0420 and new issue?

A couple of months ago, my car started shaking, with a P2191 code. I took it to a shop, they told me the fuel injectors have carbon build up and I need to replace the injectors (they just guessed, they didn't actually look at the injectors, but common issue with this car). I thought I should try to clean it up first. I took it to kia to get them cleaned. While I was waiting for the appointment, I got a new code, p0420. They did a fuel injector cleaning service and a decarb service. The next day, the light came back on, still shaking, and now, the brakes are stiff when on idle, and the acceleration is jerky. Takes a couple of seconds to move from idle. I don't know if this is a new issue or related to the old. I recently installed new brake pads, rotors and calipers as well. At this point, I feel like I've spent so much money on this car with no solutions and will probably be trying to get a new car, but in the meantime, I need to drive my car multiple times a day for work and cannot go without a vehicle but I'm not sure if it's safe to drive. Do you have any idea what the issue could be?