As a fellow 95 Disco tdi owner, there is something that might be a good idea to check, but it's a little involved: Crank pulley and woodruff keys. If the crank has some gunk in the thread or the bolt is a little stretched or just not torqued up right, the crank cog slops around a little and throws the timing out - hence the loss of power. I know it takes a bit of effort to take it off (And the timing case cover) and inspect it, but if it isn't watched it can ruin the crank.
I know this the hard way.
The good news is that if caught early, the only thing ruined is a woodruff key - $2. And to ensure correct torque on the crank bolt, the solution is to use a big HT washer to provide a couple of mm clearance.
As to timing, behind the AC tensioner you can adjust the timing a little - a 11mm drill with a 3/8th (9mm) shank will put the timing spot on in the middle. Remember to smooth it down a little with emery paper and wrap the sharp edges with tape.
That's my bet anyway.
Goodluck

