At idle on my '83 TD, I can feel the air being drawn in at the opening for the air intake. Diesel suck in alot of air as is. As mentioned getting more air isn't the issue, it's the fuel. Correct me if I am wrong, but your car has the same 603 engine that is in my wife's '87 TD. If that is the case, you have a mechanically injected engine. Unless you want to take apart the pump and mess with it's calibration, you're not going to get any increase in performance. My wife's car hauls ***. I don't see any reason to mess with it.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member