2002 Buick Park Avenue I think I need a tune up

This is a continuation of what happened when I took the car in. Don't go to Meineke! They over charge badly and messed up my car! They goofy tech crossed the wires on the coil pack for the number 5 and 6 spark plugs. That was "his" way of tuning up my car I guess. When I told them it was worse and something was wrong they told me I needed a air flow sensor, which wasn't really out, and a fuel injector on the number 6, which wasn't really clogged. Then the manager had the nerve to tell me that I should take the sensor off and spray it with computer cleaner and dump (in his actual words) "a butt load" of tekron fuel additive into the tank. But there was nothing else they could do. I took the car to Gateway tires and service center, they went ahead an replaced the fuel injector, because I had asked them to, the sensor wasn't bad at all. The tech at Gateway then told me it's still running really bad. So they ran diagnostics on it. It came up "engine misfire", The guy then noticed the wires had been crossed. My car runs fine now. As soon as he uncrossed the wires and started it, it was like a new car. By the way, the injector was starting to clog and it cost me $51.00 cheaper for the part than Meineke was going to charge me.