I have recently been expericing a burning smell in the cabin of my E46 330xi. The smell's like either oil or rubber. It happens after the engine has warmed up and sometime for just a minute and some times for longer. It is inconsitant still and, I can not identify what actions trigger the smell. I have seen grey smoke coming from under the hood, and when i pull over i cant find where it is coming from. My oil level is consistant and non of my belts are rubbing. I am assuming that there may be a small oil leak and the oil is buring off on something under the hood but as of yet cant seem to identify it. Has anyone else experinced this? or have any suggestion for common trouble spots to check? Any help would be appriceated. Thank you in advance.