ok .. then the maf sensor is probably still ok
sound like the right direction
any smokey exhaust symptoms ? .. e.g. black smoke on acceleration
when checking the vacuum hoses .. cast an eye over the turbo vacuum reservoir as well
( that's the blimp like object ) .. some pics here of the vacuum hose circuitry
https://www.landyzone.co.uk/land-rover/where-does-this-go.223312/#post-2536215
another thing to check would be the state of the turbo vacuum solenoid filter
usually changed every 12k miles ..
although the vacuum cleaner sound symptom sounds like either an intercooler hose
or vacuum hose as you've mentioned
btw: i can't comment regarding towing trailers with the td4 .. as have never done it
weight in mine .. be just me and my 18 kilo muttski staffy dog ..
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~