If the tensoner doesnt squeek dont waste the 80$ to replace it. And dont waste your money on door seals. Do they leak? No so dont do them. When they leak do them. im just trying to save you money and its not like if it starts leaking you cant drive the car.
If its not broke dont fix it.
You need to do is 02 sensors, and check over entire vehicle. Then from what you find broken replace that.