I have the following CEL codes P0171,P0441,P0440 on 99 RX300. I have replaced the O2 sensor about 1 year ago as well as the MAF sensor. The exhaust sounds like there is a leak some where. Which I will take it to a muffler shop soon so they can take a look at the exhaust. Please advise as to what can be done to get rid of the CEL codes. All help is appreciated.