its really hard to hold any sort of "controlled" driving here in pittsburgh but ive noticed an increase in mpg after i applied a set to my A4. my particular set is from
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and for $20 invested plus color matching to the car i couldn't be happier. im still gathering intel on completing the underbody of the A4, and i was looking to dimpling the surface to help w/ flow. ive seen it on some mercedes, and i think some lexus