Johan - I agree. I am taking it to Overland Cruisers this week for tweaks to the fuel pump, and it already has a stainless steel exhaust fitted. Will also investigate any worn bushes and replace if necessary.
If that makes a significant improvement then I will keep it and carry on, if not then I think I will put it up for sale as for the right person it would make a fantastic base vehicle, but it might not be right for me. If that is the case I will probably pick up a diesel LR3/4 Commercial and kit that out instead...
Size of the exhaust matters. Not just if it is SS. Also how it is routed and installed. If it has restrictions, that will limit it. One thing to remember about a diesel is it likes to breath. The more air coming in and the free flowing of exhaust going out give big improvements. A better turbo also gives great results and basically will determine how the engine runs in terms of power. IE, when does it boost and when does boost taper off. More fuel is good but if you just give it more fuel it often makes it run hot and creates more soot out the tailpipe. It is all a balance really of these things. An intercooler is also very good for a TD. It does great to help keep the EGTs down. It also makes for a cleaner bigger explosion. There is other mods you can do too like water injection but these are the basics to get dialed in if you want the TD to be just right.
The great thing about a diesel is it is much lower maintenance. It is also a very simple motor, it only needs compression, fuel and air to run. Modern diesels are more complex with a computer, ect ect but still more basic that a gas engine. Fuel economy is also usually better. Many guys here in the states would kill to have your TD 80-series.
Caster has a lot to do with how the steering feels. If it is out, even by just 3-5* it will feel sloppy in the steering. It will wander and drift and not be responsive. When I got my truck it had a big drop bracket on the radius arms up front to correct caster. I lifted the front end 2" and removed these drop brackets. My caster was then out by 9*. The truck drove awful, sketchy even down the hwy. I fixed the caster, getting it even a touch beyond factory specs since I have 35" tires. I put in a custom built steering set up, all new parts. Now it drives like a brand new truck and I can 2-finger it down the hwy at 80mph. I wouldn't even do 80mph in it before this as it was just to sketchy. So while yes you need bushings, tres and so forth to all be in good condition and not worn out, there is more at play if the truck is not stock.
I am a fan of a coil sprung solid front axle truck. It is simple, stout and coil springs are cheap. It is also easy to work on. New coil springs and shocks is cheapest in this kind of truck. With IFS, nice c/o's are not cheap. Leaf springs also cost more than coils to upgrade. Nice leaf springs can run $1000 per axle. C/O's can run upwards of $2,000 per axle. Top of the line coil springs, $250 per axle.
Cheers