An in line filter needs to be placed away from the hot parts of the engine, many are mounted next to the carb which is poor as they get heated and cause problems.
Are you sure your servo is not right? Where have you found your info on upgrades?
There was more than one type fitted in the 80's. A talk with John Craddocks parts could be useful.
It does sound like there is some sort of restriction in the fuel supply.
When you pull out the choke you get more draw/"suck" [trying to keep this basic so you understand] pulling fuel in but the air supply is also cut down. Result engine runs rich but not as rich as it would when running...
It may be your early basic "New Defender" may be the best of the bunch. Recent reports of those sold in the last eighteen months of a good number are having costly repairs if it was not for the makers guaranty. Now extended to 5 years, I wonder why?
Would have helped if you had said what model truck you have to start. But as I noted above do at half tank and you have a chance of getting it right. Good luck.
With my 77 Series 3. You normally pull the stop out first to stop the motor, you have to hold it out until the motor stops running and then let go the stop and it returns to the run position ready for next time.
If you switch off the ignition key first most electric items stop but engine keeps...
That is standard for 93 110 as regards engine. The term "direct drive" I have not come across regards the Land Rover engine. Can only think it is with regards Zuse gears as noted in above post. Have a look at "Landrover forum uk" for more info about them.