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      12-28-2012, 02:04 AM   #6
Second Lieutenant

Drives: 2010 335i E90 Lci N54
Join Date: May 2012
Location: San Jose

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2015 F82 M4  [0.00]
2011 F10 535i  [0.00]
2010 BMW E90 LCI 335i  [3.75]
Originally Posted by shiv@vishnu View Post
There is nothing that would cause a reducing in fuel economy other than your right foot, tune or no tune. If you drive both an untuned and tuned car hard, the tuned car will get fewer mpg. Both driven casually, they will see the same fuel consumption.

One thing you can check is to make sure your o2 modifier wires are removed in the harness as newer DME software versions took offense to this function. And this could possibly cause poor fuel economy. All of the harnesses made in the last 2 years have had these wires removed. But it's worth checking to see if you still have it installed.

See here for more info:
this is my procede
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