NHTSA Complaint #11626365 — 2008 CHRYSLER 300

When taking vehicle for test drive about a month ago, the check engine light was on and after driving it, i noticed when AC was on and when off, the car loses power. When i go to pull out it has no power and i almost got hit in the side every time i would pull out from a busy highway. They had check engine light looked at and they said computer told them it was air valve leak or something like that. I had appointment for them to further assist and they said they could not find anything wrong. I can hear where the valve might be leaking at. The brakes are not good. I had to put on the brakes today fast and brake pedal acted like they were gonna skid out from under my foot. Brakes are new so why is it acting like i have no brakes and there is barley any acceleration. Something is going on and i don't want to be in a car accident just because our warnings are being over looked.