These old Quantums/Dashers/Passats/Santanas are indeed surprisingly fast. The older, the faster, at least in Europe. They are lightweight cars -the oldest brother, the Audi 80 B1 was indeed deliberately as a lightweight-car constructed by Ludwig Krauss and his team.
With "at least in Europe" I mean, because the pre-catalytic converter-versions (before 1985/86) are faster than the later ones. They aren't that worse castrated as the mid-70ies-US-spec cars (all cars, not only VW's), but despite the catalytic converter, injection and ignition had a different adjustment.

I remember my high-speed experiences with my Dad's 1981 Passat LS [32B]. It was just the semi-basic 75 hp-1.6 liter-version, but the older it became, the faster it was going. No catalytic converter and the "angle-grinder-stylish" 165-tires were very helpful. Officially its max speed was 164 km/h, so I was really surprised, when I saw the first the needle at the 190 km/h-line while driving full throttle down a hill
Later I've seen, that the Passat became faster, the more I drove long distances with higher speed on the Autobahn. At its last time it became so fast, that the tacho-needle clicked, far behind the 200 km/h-line ( as here, the basic tacho without a rev.counter: http://www.gebrauchtefahrzeugteile.de/images/product_images/popup_images/2903_0.- jpg ) against the knob for the "0"-position of the trip counter


It was a really nicer driving, when the valve-shaft-rings were leaky.
The blue smoke due the burned oil, was very usable to keep annoying BMW-drivers behind on distance. They came along and wanted to push the shabby old VW away from the left lane. I let them coming closer, still driving full throttle, then I lifted the foot off the gas pedal and then, after a few seconds, I kicked down the pedal two times suddenly fully down - there was a complete blue wall behind me And noone was hanging at my back anymore.