Hi, I am also interested in the diesel conversion. I have another diesel truck a land cruiser using a 4.2 TD engine. There is a slight lag initially but catches up with the Vx and overtakes it. The truck is still tuned for soft driving, ie. no boosting nor playing with the fuel pump.
The plus side in Malaysia is that diesel is about 1.35 USD / Gallon. I'm currently discussing this conversion with a friend so far it seems promising. Trooper in Malaysia is the "Government Choice" vehicle. So Isuzu diesel engines are easy to find.

Ameet