Air Assist SUCK MY ASS!!!....
...It's purpose is to increase mileage.
No biggie but I am pretty sure it is the same purpose as later model TGV's which is to improve cold start and low RPM/idle emissions, not necessarily mileage. It's all part of the SULEV (Super Ultra Low Emissions Vehicle) directive. REF Granted SULEV itself pertains hybrids but the technology is swapped to non hybrids when applicable.
I know this because I briefly worked for Delphi as my senior design project back in 2005 and helped to design the TGV actuator for the current model Ford V8's. I can only hope that now Mustang and truck guys alike do the same thing we all do and rip those things out.
i agree with both above ^^ that wiki page is the only good Subaru VIN decoder i've found, and opposedforces is the site i use the most for part numbers. i wish i knew who owned the site so i could give them a high five!
10,000 RPM Tachometer - Was an option part sold by STI. They made versions for ver 4 (1998) and for ver 5/6 (1999/2000), and they are not interchangeable (reference link).
Impreza RS Sports Package - 2005 - Received all WRX interior minus the boost gauge and gauge cluster. This included WRX seats and 6-disc cd with an upgraded sound system. Not sure if this was offered on the 04 or 06 - present models.
[*]Version 4-6 JDM WRX & STi
Model years can be tricky in JDM, as they usually lead USDM by a year, but not always. Ver 4-6 would be 1997 (maybe 98) to 2000.