As has already been stated 'Ventiler' simply means 'valve' . There are 4 models of 944 - 8 valve, commonly known as 'Lux', comes in 2.5 and 2.7 varients, 'S' 2.5 16V, 'S2' 3.0 16V and 'Turbo' in 220 and 250 HP varients (and designated 951 by Porsche - purists will insist they have a 951 not a 944 Turbo

)
The 8v and the 'S' are visually identical (the only way to tell quickly is to pop the bonnet and look at the cam cover and airbox) and as such it is not unknown for unscrupulous individials to stick an 'S' badge on a lux to trap the unwary.
As to rarity, well it was only in production for a couple of years so there are naturally fewer around, and as previously mentioned they had a bit of a bad press (unfairly in my view). I had one for 3 years and drove it every day. Make sure your engine is sound, then get it over 4K rev's and keep it there to get the best out of it
