2006 Frellander TD4 speed sensor problem

Hi. I have had a problem with my Freelander, when the engine reaches temperature it seems to lose power uphill, it almost feels like a airpipe to the turbo has failed. I have checked the pipes and replaced one but this has not improved anything, I replaced the MAF sensor and that did nothing and then replaced the air temp sensor, still no improvement. I have checked for any fault codes and it comes back with P0500 speed sensor A.
There are no dash lights showing to indicate any kind of fault.
Now the crunch is, what is the correct speed sensor, some say its the one in the offside front wheel hub, some say its in the rear axil and others are indicating it is in the autobox.
Any indications where and what it is would be appreciated.

P0500 is a generic ECM code for any several speed sensors. You need a full systems diagnostic to identify the exact cause of that code.
There are two speed sensors in the gearbox, one in each wheel, so you need to run a diagnostic on the TCM and ABS module, if you want to identify the cause.
It's probably unrelated to the power loss issue. The LP fuel pump on the other hand can cause low power.