Land Rover Repair: Power Loss, discovery td5, filter clean

Question
I have owned a 2001 Discovery TD5 automatic for the last 12 months.  When I use it for towing, I lose speed on hills.  A friend of mine also has a Discovery (1999 manual), but on hills, his car out performs mine under the same conditions.  Is this normal for automatics to lose power more than manuals, or could their be other reasons which need to be addressed?  The car has been serviced at Landrover 3 months ago.

Answer
The two vehicles should have similar power.  Are your fuel filters and air filter clean?  Do you have the same tires, and vehicle configuration?

If so, I'd suggest you have a local LR expert drive the truck and see if he thinks it really lacks power, and if so, why.