due to lack of room on the ZD30 and i hate cutting bonnets, i was looking at water injection. properly far cheaper but water useage is fairly high so you need somewhere to fit a decent size water tank. i was looking at at least a 20 litre.
i rekn you could mod the denco to fit as a top mount. but theres prob a kit out there for a top mount.
the CRD ones they changed the way the mounted the IC and i think they have less problems.