For the ED30 at least, VW quote 14 bar on a new engine. I tested mine (hot) a few years ago and that is what it measured across all 4. That was with a cheap Gunson tester from Halfords though, so not sure how accurate it is, but the important thing is consistency across all cylinders, not necessarily the numbers.....so long as they're above VW's minimum.
K03 engines have a higher compression ratio, so might show a little more on the gauge.
Someone on here a few years ago was in the same boat. Old engine....sell up and move on, or invest in stage 3. He ended up buying a brand new CDL engine from TPS and a TTE420 turbo. That's a £6.5K chunk right there before even getting into the mapping and other supporting mods, so it gets real expensive, real fast!