[euromodder]

The roofracks (especially the transverse carriers) are already gone, I hope ?

The ridge on the front bumper cover may save your paintwork, but it isn't going to help your fuel economy.

Removing the mudguards aft of the wheels will help a bit.

Exhausting air through the wheel wells may very well work against you rather than improving your mpg .
Then again, it is being done (by BMW, IIRC) to lower the drag, but they have the slight advantage of a wind tunnel to test how and where to exhaust the air.