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FWIW: Here is the (only slightly technical) explaination I got from a Volvo rep about manual transmissions, turbos, et al.:
Automatics are never a huge problem, because the ECU is always capable of adjusting both sides of the equation (Engine/Transmission) to keep emissions under control while maintaining a safe level of power. With the LPT engine, they are right on the edge of emissions. The vast majority of their sales are automatics. This is where they spend most of their efforts initially.
Manuals are no problem in terms of emissions in a normally aspirated engine. The ECU can keep them under control in most all circumstances because of the predictable nature of the normal aspiration.
High-pressure turbos with a manual are a little bit of a problem, because they have the capacity to burn (or not burn) much more fuel under boost. But becuase of the reduced compression ratio, and larger compressor of the HPT, they are able to do some magic tricks with the ECU and scrape (barely) under the wire with emissions while not endangering the driver. (It's not immediately obvious to me why the compression ratio makes a difference, but apparently it does.) At any rate, they sell less manuals than autos, even with the HPT. The HPT Manual version of any new product will normally be the last product released in the US, primarily for marketing/demographic reasons.
Low-pressure turbos with a manual transmission cannot pass EPA emissions requirements. Volvo engineers say they just can't make it work at a reasonable cost due to the properties of the LPT engine. This is the killer that we will apparently never see in the US: An LPT engine with a manual transmission.
In order of "ease of engineering to meet EPA standards", from easiest to hardest here are the combinations:
1. NA Auto
2. NA Manual
3. HPT Auto
4. LPT Auto
5. HPT Manual (Borderline)
6. LPT Mabual (Over the line)
This all sounds plausible to me, so I bought it -- but the information is probably worth about as much as I paid for it, so all standard disclaimers apply.
The best news is that the 2000 model year C70 Cabrio is now available with HPT __**AND MANUAL**__ !! I could be in big trouble if I ever happen across one of these on my dealer's lot. :^)
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