Loss of power after traffic or when towing

Hi all
I am suffering from a terrible loss of power when towing and after traffic when solo. No codes to read when stationary but random gear box ones like gear ratio errors if scanned during motion. Most popular gear box error in motion is transmission over temperature. I wonder if there could put the car in a safe mode without putting a warning light on. I wonder if my changing the atf using standard atf-s rather than land rover magic fluid could be the cause??
By the way Maf and map values are sadly bang on what they should be.


Thoughts appreciated.

James

Just in case anyone else gets this.. the reason was the wax valve in the fuel filter being stuck.. this causes fuel to overheat and a non code throwing loss of performance through pump limiting fuel output.
Cheap fuel filters have cheap wax valve!

More detail here
https://www.freel2.com/forum/topic34191.html

jtq4u said:

Just in case anyone else gets this.. the reason was the wax valve in the fuel filter being stuck.. this causes fuel to overheat and a non code throwing loss of performance through pump limiting fuel output.
Cheap fuel filters have cheap wax valve!

Click to expand...

That's correct for a Freelander 2 diesel. Unfortunately in your initial post, you didn't mention what the vehicle was, which probably explains the lack of replies. Thanks for the update.

For reference, the only fuel filters to use should be marked Perflux, which is the OE filter.