BMW Repair: Error Code P1158 & P1160, vacuum leaks, fuel mixture

Question
I received a code P1158 & P1160 for my 2001 740i.  I drove to lunch and then when I started it back up my service engine light came on. I was planning on having my oil changed that day so I had the mechanic look at it and he got these codes, but could not find anything wrong.  He went over everything he knew too.  I just moved to a new town, so this is a new mechanic to me and so I am a little skeptical that nothing is wrong.  I cannot imagine getting those codes if nothing was wrong.  The mileage is at 51k. He cleared the code out and I have not had any issues with the ses light since, but I am just concerned that something is not right.  Is there an issue that is common which I should have checked more?  

Last 7 of VIN DN86123


Answer
Dominic, These fault are for addative mixture both banks. BMW fault codes 28, and 29 for DME ME7.2 control module. Usually the fuel mixture is too lean. Check for vacuum leaks, intake manifold leaks, rear manifold backing plate diagrapm damaged, etc. Check intake duct work and connections.
-Evan