Summary : My exhaust rusted at the rear axle and broke a few years ago. Decided to finally throw a new exhaust on and the car feels different. Feels a little slower. With that said, it felt VERY different around 65 mph on the highway, I can't think of any words to describe it. Car seemed fine 0-60 and 70+ mph, but right around 65 felt WEIRD.
I don't know where to start.
What should I start doing my research on? Back pressure? O2 Sensor? If its running lean? Fuel pressure or pump?