car surging when slowing down

I recently purchased a 2004 E320 and just months afterwards noticed that the car would surge back and forth (like I was driving a 5 speed and did not put in the clutch) when I would slow down to stop or when driving through parking lots at slower speeds.  It is currently at the dealership (for the 5th time for the same issue) and they claim that there is nothing wrong with it since they can not feel it this time around.  They also claim they fixed when the replaced and adjusted the clips in the transmission last week.  The also replaced a torque converter and loaded some upto date software that was needed.  Of course all of these things done on seperate visits to the dealer. 
Any ideas what this can be?  Any help or advise would be great.  Could this car be a lemon? 
On a side note, any idea why a tire would go flat 3 times within the past 2 months but the dealer nor the tire shop can figure out why?  Yes and now the dealer wants $180 for a new tire that was supposely new back in October when I bought the car from them.
Thanks in advance.

generally, this sounds like a mass air flow sensor problem ,,,go to getcoolparts.com buy the bosch, dont get the meyle,,,its cheaper but doesnt work right i know i had the same problem,,,,about 207.00 ,,this should cure the problem,,or it could be two other things,,,bad catylitic convertors , egr valve which is not expensive, as to the convertors,get after market better flow converters at a muffler shop,they let the car breath better,,,i would start with the mass air flow sensor,which is right after the air filter, just unplug the wiring clip, take out replace real easy,,,try that first

Mass air sensor out of range enough for you to feel it affecting drive quality it would trip the typical p0170 and p0173 codes and a check engine light.Always clean a mass air sensor if you have a code to see if that solves the issue and turns off the light.CRC brand maf cleaner.
Look for vacuum leaks in the intake system.
bad cat would also throw a code and is covered for free if that was the issue.
BTW save yourself 50bucks when you do need a mass air sensor
www.autohausaz.com has oem bosch for $40 bucks less then the above mentioned web site and free shipping over $50.Getcoolparts.com is way overpriced...........
ohlord

I had same problem on my 03 when I first bought it, most noticeable when I was in a parking lot or somewhere else at low speeds. Dealer said to try fuel injector cleaner, which I did. Also, said I need to drive it for a while. They claimed that the tranny was adapting to my driving habits. After about a month it stopped. Two months ago I put larger staggered wheels on it, and went through the same thing again. Took about a month and a half to go back to normal. Hope this helps.