There is very little wrong with a post '93 VW diesel, provided that you get
rid of the EGR which is all but useless. It has larger swirl chambers,
hydraulic tappets and a cambelt tensioner separate from the water pump. In
TIC form it gives 122 bhp from the factory but can be tuned quite
successfully (VW got 225 bhp from this engine) with a quite enormous
increase in torque compared to the 2.5 Audi/VW five cylinder offering. My
own car is pushing out 145 bhp and is difficult to hold back to 60 mph when
towing my caravan on motorways. I kept up with an empty articulated vehicle
(owned by Norbert Dentresangle) in third gear on the southerly exit from
Chepstow, which as you may or may not know is quite steep whilst towing my 1
ton caravan.
However, there are several diesel engines that should fit with a little
engineering know-how, such as Mercedes, Toyota, Nissan. I am sure that if
you could afford one even a VW V10 diesel will fit nicely, or even the V8
Audi.
All the best, Peter.
700/900/90 Register Keeper,
Volvo Owners Club (UK).