I had a Scangauge II on my 07 CRD and it was virtually spot on for fuel, speed, coolant temp, boost etc once calibrated.

IMHO instantaneous fuel is of little value so I didn't use it much at all after first getting an idea of how much throttle meant how much fuel is being injected if that makes sense
This meant I found out that the CRDs (well, mine anyway) like to be driven harder and give better economy if accelerated firmly up to speed and then cruise along rather than Miss Daisy style driving.

When I set mine up it did have a "Diesel A" and a "Diesel B" setting, one gave stupid numbers and the other spot on.
The book said try one and if it doesn't work try the other.
Dunno if the Ultragauge is the same tho