codes p0141 and p0161

I have a MB Ml430 and the check engine came on, pulled codes and they are P0170,P0173,P0141. So I bought 2 O2 sensor and installed them both. Still getting code P0141 and now P0161. I removed the EGR tube and cleaned it, it was about 50% plugged. Had codes erased and they came back. Check resistance on old sensors 2.7-2.8 ohms will be compare to the new ones this weekend. I have done some reading up the actual code it looks like just a heater circuit issue. I am looking for something else to try. I am going to check the wiring also. Any help or hints would be appreciated.

Hey friend, what year is you vehicle and where did you get the new O2 sensors? O2 sensors are not something to buy from the cheapest place. Do you have a scan tool? If so, you can observe the sensor voltage and see if the new ones are working.

I have a 2000 Mercedes ML430. I bought the sensors at Oreilly's auto. After doing more research I looked up the sensor on autohausaz and they showed a different sensor part # than Oreilly's. I called and talked to them and ask what is the difference between the 2 part #' both are Bosch Oreillly 16123 and Autohausaz 15202. The guy from Autohausaz indicated that the sensors from Oreillys is for model year 2001. So I have bought the correct sensor 15202 and hopefully I will have them by Monday and get them installed. I will return the 16123 part back to Oreilly's for a refund, Oreilly must have a error in their database because it shows 16123 for model year 2000. I double checked with other stores like autozone and advance and they agree with autohausaz as to what is the correct sensor part #. Hopefully this is the problem.