Just a quick question. When I get below a quarter of a tank of fuel it seems to drive sluggish. I've noticed that if I remove the locking fuel cap there is a vacuum. Should there be or has the previous owner fit the wrong cap without a breather in it.thanks

Don't know if its related, but I once had a Range Rover that when the tank was low, OR going uphill, OR rapid motorway speed; the power went off and/or started jerking. Took it a LR dealer in Amiens, France en-route to Spain...they found dirt in the fuel tank. As soon as fuel level gets low, the sludge congregates around the exit filter. A drain down and flush through rectified the problem for a trouble free holiday.

I do remember there being a vacuum when filling up, not always, but often.

If you have muck in the tank you could be in a world of pain, the tank is actually two tanks in a saddle design that are joined at the top, with a pump that transfers fuel from one side to the other. it doesn't have a drain, so cleaning is a tank-out job.
Not technically difficult, but time consuming, and the tank is darned heavy when it is only 1/4 full. Tangiers Orange - gone, missing her
Replaced by Ewok what a mistake - now a happy Disco Sport owner

When I bought my current FR2, there was quite a vacuum in the tank but I didn't notice any problems when driving. When filling up, there was a loud 'whoosh' when I removed the filler cap. I bought a new cap and cured the vacuum. The only difference that I could see between the two caps was that the new one had a purple coloured inner. 11 GS Bali Blue
07 GS FL2. Usually muddy. Gone
Numerous LRs since 1963