Here we go
Taken from a *cough* Jetta owners club site

At the beginning of 1981, when Volkswagen announced a series of energy-saving measures under the banner of Formel E Technology, the Jetta, like the Golf, became the recipient of an optional 3+E gearbox in which (fourth) offered a cruising gear in which the engine revs typically dropped by around 1000 rpm following the change up from third. The other Formel E equipment mirrored that of the Golf, but with the addition of a rear spoiler.