For 160$, buy your own scanner.
Can you list what all they did for that cost?
Even though you have low miles you have age.
Goto just about any parts store and loan a tool or buy one.
Odds are if you can't feel a change then it's something that the car has adjusted to already. So it could be the VCT or a bad O2 sensor or maybe the timing was not done right with the cams. or maybe the oil stick is not in tight, or maybe it's just a gas lid open circuit and so on a so forth blah blah...
