Some of the Golfs had the 2.9 as well - I was going to buy a 2.9 with a bored out engine dyno'd at 209BHP or something but the owner ended up changing their mind on selling it. (Probably wasn't a good idea to buy it anyhow - likely needed more enthusiast/dedication running it than I would have been motivated to put in).
That engine would have been swapped. No mk3 Golf's came out of the factory with the 2.9 engine. The Corrado was the first VW to get the engine which was originally a 2.9. But there were some reliability issues (I can't remember exactly what but bore ovalling comes to mind for some reason) so VW reduced it to a 2.8 for the Golf. The 2.9 did put out a small amount more power so it was not an uncommon swap if the Golf engine died for any reason.
Corrado VR6 - 2.9L 12v (190bhp)
Golf mk3 VR6 - 2.8L 12v (175bhp)
Golf mk4 V6 4Mo - 2.8L 24v (204bhp)
Golf mk4 R32 - 3.2L 24v (240 bhp)
(I've had them all except the R32)
The later 24v engines are certainly more drivable on modern roads. The 12v needs to be revved to really get the power out of it. It means I'll be sitting on a motorway in 5th at 70mph just where the power starts to come in. So, so tempting, especially with the noise the VR6 makes
VW also reduced costs at the last minute by not using their switchable inlet manifold. They had originally designed a manifold which adjusted the inlet length above a certain RPM (I guess a bit like a more modern VTEC?). But to reduce costs they didn't use it in the end. That's a real shame.