I Have an E270 CDi 2004 with 140,000 miles running a map and a tuning box,so far so good as far as reliabilty goes,i mainly use it to taxi weekends so MPG is all important.Estimate my mpg(over standard) has improved around 10%.Map has been on over 2 years and 40000 miles (map +box over 6 months)with no issues.