racing engine no oommpphh

hello new member not used to this at all having probs freelander 06 td 4when driving uphill specially when towing caravan press on accelerator engine races rev counter goes up no power whatsoever speed stays the same exactly the same when not towing though been for diagnostic told injectors 1&2 gone new ones replaced running better but still engine racing with no ooommpphh could it be sensor problem

Slipping clutch ...

Unless it's an auto and it's kicking down to lower gear.