1999 RX 300 Knock Sensor Problem

[joep54]

I have a 1999 RX 300 with 186k miles on it.  Kept getting code for knock sensors, so i had mechanic change the sensors as the car would no go out of overdrive.  Well had Knock sensors replaced and the P0325 and P0330 came back and car will not go into overdrive again.  Any suggestions on what else to try.  I have put in the Premium gas but that has not helped.  The car runs great but MPG is down and worry about log trips.  Will take any suggestions to help take care of problem or can i just  drive it like it is?