Maybe it's time to do test's that we know are wrong Disconnect the inlet air pipe from the back of the air filter - yours is a defender so it's different from the disco I have Disconnect the turbo to injector pump pipe and see the results - if nothing changes it might tell us something - not...

Another very common problem on the D1 is the circuit board - green in colour and housed in a black box - normally under the cubby hole but you have a funny steering wheel position On normal RHD cars it is mounted horizontally and there are two sets of wires plugging in and each wire set is...

1 other thing worth trying as it is easy to do is to disconnect the rubber pipe going to the waste gate and blank it off. I did that using a short bolt that screwed in nicely and some wire as a clamp - that was 7 years ago

I have a D1 and by removing the aircon belt tensioner I can get a thin long 10 mm socket onto the 3 bolts holding the cam belt pulley to the injector pump. By loosening the three bolts I can change the timing just enough to give me more low down power or high end power at the loss of power at...

Thing is adding extra fuel without extra air will only create a serious amount of heat . An egt gauge is a must if you start playing with that fuelling. It is a nut on the back of the pump - probably has some sort of anti tampering wire on it - Loosen nut and turn screw with a screwdriver...

Ideally you want a gauge with say a max of 2 or 3 bar range as the difference between .8 bar and 1 bar boost could explain your problem. Having said that I am at .5 bar at 110 kph on a flat road. An egt gauge would also help greatly in this logic maze In the absence of that maybe do a run...

On the D1 all the headlight current goes thru the in car stalk. I have only experienced having no headlights other than high beam / brights. I don't have the HID's you do and I drought you are washing the interior . I also cant turn the vehicle off if the lights are still on in mine 97 300 tdi...

Those marks are strangely evenly spaced

On the hoses - I have had a set of britpart blue silicon hoses in for at least 15 years - they are worth it if you need to buy hoses anyway

That sounds like the boost isn't getting through to push the plunger down on the fuel injector pump- forget it's proper name now. As too why it is intermittent that is a mystery - A boost gauge T'd in just before the pipe goes into the injector pump might give you a clue

I have those in my D1 so can't comment on the springs dislocating But for better articulation you might want to allow each bag to be connected to the other bag . I think a valve might be required to stop this airflow for use at highway speeds though

Didn't know it was possible for water to leak there As mentioned the water pump sit's high and the dash heat gauge is useless as by the time it moves it is tickets allready I run a water level sensor in my expansion tank and has saved me many times from overheating

What is a valve port ?

Alway's been called that in saffaland

There is another one of those welsh plugs at the back of the motor - which would leak down onto the g box