help!! trouble codes
 

hello all i have a 2000 ml320. i recently had several codes come up for check engine they were all related to o2 sensors and egr . so i took out the egr cleaned it up made sure it wasn't stuck or anything, i was not able to get the egr tube out to clean it because of its weird bend on it i played with it for 45min before i gave up and just put it everything back together. i also changed the o2 sensors that were giving codes which were the post cat sensors(rear) with new ones. so when i turned car on drove it for a while nothing no codes, then next day woke up drove it for a bit then engine light came on again. scanned it and p161 and p0400 came up so thinking egr might be causing all the trouble not sure where to go from here guys. need a little guidance here if anyone can suggest anything or something im missing, common problem anything?? any input is appreciated thanks everyone ..

Search this site and Google, and you will find lots of posts of exactly your situation. I didn't read through all of them for the solution. One suggestion is to replace all O2 sensors, with the logic that they are old and likely need replaced. Then go from there. I would replace any EGR hardware. Buy a repair manual so you can to the proper disassembly of the EGR components.