Smoking/ sluggish probs

Hi All,
As I am new to this sort of thing was wondering if someone could give me some advice on my Freelander TD4,(52 Plate)
She has given me no problem since I purchased her, however I needed to move my sited caravan recently for service work and noticed that she was smoking heavily when required to work a little harder, ie hills etc, Also I use her to tow my sons Horsebox (Ivor Williams) with a medium sized cob, approx 500kilos, overall about 1500kgs, again she has started to smoke when under a little bit of strain, the turbo kicks in but she feels a little more sluggish and requires more gas to get her going, any ideas?
Forgot to add, This has only just happened, this has not been the case in the past when towing using her.

check / clean egr valve, also check all the intercooler hoses for splits and so on, esp where long one passes across the front of the top of the engine and chafes on the mounting screw.

good luck