Below are some threads from the now-defunct “Toyota Van People” forum dredged from Google's cache. This is by no means all of the great information that was once there, but what I could find a week or so after the site winked off. This is almost all from the Previa Tech forum, too.

TVP is apparently gone, but will soon be replaced by Toyota Van Tech

A discussion of SADS rebuilding options

A view inside a Previa automatic transmission

Cold Start issues

Throttle Position Sensor (TPS)

Previa Special Service Tool source

Typical Previa issues to be aware of

Previa heater blower motor/switch issues

Battery terminal issues to watch for

Collision catalog – part numbers galore

Tim's tricky heater core replacement procedure