Don't mess with it - the car already has a pretty large airbox, assuredly bigger than the 121HP it is asked to support. With a Diesel, you need more air AND fuel, so enhancing one without the other (and I doubt this would increase air intake) is useless

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"If God had meant for us to walk, why did he give us feet that fit car pedals?" Sir Sterling Moss

Michael
2014 E63S Estate
2006 SLK55
1995 E500
1986 Porsche 944 turbo