So last Friday, while driving to work, I noticed my 300D (1983, 240k mi) sounded... great! Beefy and throaty under load, and I could even vaguely hear the turbo spool up at times. It was a treat.

Normally, the engine sounds fine, but not great. Standard 300D fare.

So the reason it sounded so great was because the turbo's u-tube became disconnected from the air filter housing. Turbo was sucking in hot, unfiltered air through the u-tube.

How can I reproduce the sound but still properly filter the air? I've heard that the stock air filter set up is about as good as it's gonna get (filtering-wise), and the "high-flow" cone filters are comparatively pretty crap (plus you'd have to reroute the valve cover breather tube).

A "high flow" setup may not even reproduce the sound, but if it does, how much would a "high flow" setup negatively affect longevity?