I've mentioned in a couple of other threads on this topic that I think the $100 is for an extended warranty on a bunch of engine components. In the Federal Emissions section of the manual, this stuff is spelled out in a lot of detail. In there, it is pretty clearly stated that none of the fuel delivery components, and very little of anything else that is not contained inside the engine block itself is NOT covered under the 100k powertrain warranty.
This section details the following stuff as 2 years or 24,000 miles:
EVAP Canister
EVAP Canister Purge Valve
Mass Air Flow Sensor Assy
Three Way Catalytic Converter
ECU and Power Supply Relay
Electronic Feedback Controls, Sensors, Switches and Valves
Exhaust Gas Recirculation System
Exhaust Manifold and Gaskets
Exhaust Pipe Up to Catalytic Converter
Fuel Filler Neck Restrictor
Fuel Filler Cap and Gasket
Fuel Injectors, Fuel Injector Lines and Fuel Pressure Regulator
Fuel Tank
Gravity Check Valve
Knock Sensor
Malfunction Indicator Light
OBD system
Glow Plugs
Diesel Fuel Injection Pump and Associated Controls
OBD Date Link Connector
Oxygen Sensor
PCV Valve
Charge Air Cooler
EVAP Leak Detection Pump
Turbocharger and Wastegate
Secondary Air Injection Pump and Associated Controls
Emission-Related Hoses, Gaskets, Clamps and other accessories used with the above components
For 8 years or 80,000 miles the coverage is only on the following:
Catalytic Converter
ECU
OBD Diagnostic Device
The "California" Warranty extendeds the coverage for a lot of the 2 year stuff out to 7 years or 70,000 miles including (for the TDI):
Catalytic Converter
Charge Air Cooler
Exhaust Manifold
ECU
Fuel Tank
Intake Manifold
Transmission Control Module
Turbocharger
Diesel Injection Pump
There is also a statement in the front of the Emissions Section that basically says that Vermont and Mass. have the same coverage as the California cars.