This article is from the VW Performance FAQ, by with numerous contributions by Jan Vandenbrande others.
A:There are four major auto-x categories: Stock, Street
Prepared, Prepared and Modified. It is relatively
important to avoid spreading the misconception that the
four categories are a linear progression -- they're not.
Modified is not for "production based cars that have been
modified beyond Prepared allowances," because that
suggests that Prepared is beyond SP, and Mod is beyond
Prepared. It's not so. It's better to think that there
are two progressions -- Stock -> SP -> Mod, and Stock ->
Prepared -> Mod. I generally phrase the Modified
description as "two for production-based cars that only
barely resemble their original configuration."
 
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