Audi S4 C4 was a fast version of Audi Cpp C4. Later similar model got the name Audi S6. And actually, present Audi RS6 C8 are descendants of this Audi S4 Avant C4 with swapped V10 5.2-liter engine. You could find such V10 in Audi R8 or Lamborghini. However, from beginning Audi S4 C4 had 5-cylinder 2.2-liter engine. So, this car has enough space in engine bay for such swap. But it doesn't mean, that it's an easy walk to swap such engine.

I am not sure these cars were present on American market in 1990s. So, I guess this car is already older than 25 years, that's why it was imported in US. And now we see this Audi S4 C4 with swapped V10 engine with New Jersey number plates. I don't know when did this mighty 5.2-liter engine was swapped. Hope this Avant has saved all its functionality, including Quattro. It may be really fast vehicle, because that cars were not so heavy like modern. By the way, this Audi may have just insane exhaust sound!