Belt Change, messed up my car little bit Options

[alx22ua]

I have a little problem with my top speed, and how the car accelerates. I had my timing belt changed just resently, the damn thing snapped when I was going on a highway, thank God the valves weren't bent, so I payed about 400 dollars for the repair.

Now however when the car accelerates and reaches 4500rpms, the motor does not go any further, and it feel like it brakes the car (you know like when you go downheel, when your car is still in gear, you dont give your car anough gas, so the engine brakes the car), it feels exactly like that, only much stronger.

I've been thinking about it, and I think when they put in a new timing belt they put it on too tight or something, so it does not allow the car go above 4500rpms, also I remember they were messing around with ignition timing, that could also be a problem. What do you guys think?