Bought this car has a 3.4 guy just had trans. Flush and filter done at a shop before had done car ran fine after trans. Slips. First thing in morning doesnt move real easy when warms up lot better and also notice more slipage when turn to left. Then if you drive on hwy. Say 50 miles then enter town to a stop light rpms raise and lower up down' let car cool then just fine. Had codes scaned yesterday has an o2 sensor code thats it. What might be the prob.