I've read a little bit about the ALDA, but from my understanding of it it can only affect acceleration and amount of smoke, not how the engine sounds, though I'm not sure about that. I hardly get any smoke from my exhaust, except for a few seconds after a cold start, but I do get a pretty loud but consistent diesel knock at idle across all cylinders. Above 1500 rpm or so it's as smooth and quiet as a gas engine even at this high elevation.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL