The dealership told me that the o2 sensor needs to be replaced, which o2 sensor would cause the car to bogg and lose power, the exhaust or the manifold sensor? They both look the same!
I have any aftermarket sensor, im not sure which one i should replace.

 

It would be the 1st one that controls the fuel trims. That's most likely your problem. To save a bit of cash and remove some of the symptoms quickly, you can swap the two sensors around. The 2nd one is not as important to vehicle operations as the first.

 

most of the aftermarket o2 sensors doesnt work that well... are you getting some cel codes? what were they?

 

^^ one of these days I'm going to rewire things and make those cheap as hell aftermarket o2 sensors work.