Turbodiesel engines run with an excess of air already. I.e. the stock intake and exhaust systems run more air through the engine than it can use---power is determined solely by the amount of fuel injected. It's not like a gas car where you can open up the intake, slap on a less restrictive exhaust, and thereby gain a few horsepower while keeping the air/fuel mixture constant. From a gas engine point of view, diesels already run lean---so more air does nothing.

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AlexTheSeal: hack mechanic, inadvertent drifting champ, builder of infernal devices, professional epistemologist

'87 300D Turbo, roadtrip mileage champ (for sale!)
'92 Isuzu Trooper, mudder extraordinaire (for sale!)
'82 Honda Silverwing, cockroach of motorcycles
And various boring daily drivers...