I have a 99 9-3 2.0HPT SE and my Girlfriend has a 00 9-3 2.0LPT base. My observation is based on these two cars. I would say my 99 is quieter as far as actual mechanical noise is concerned, however the 00 seems smoother and definitely gets better fuel mileage. The 99 also makes about 75 more horsepower, so that comes into play on the fuel mileage. I tend to use the "happy pedal" quite a lot, my girl, not so much! I'm betting that the lighter rotating and reciprocating mass of the 00 makes it smoother and contributes to the economy difference.Thanks guys.
I asked this because I had red the T5 engines were supposedly even quieter than T7 engines thanks to the "extra" soundproofing as they´re more "overbuilt".