Towing Issues with 91 T/D 80 Series

I've just returned from my maiden voyage towing a 19' Jayco Expanda. I found that my 80 series diesel, fitted with factory turbo, struggled at times towing the van. Being a manual, I never went into overdrive (5th gear) so it was revving around 2800 rpm sitting on around 90 - 95 kph. The car would struggle up hills and would over heat under load, as well as emit significantly more smoke from the exhaust that it normally does. Fuel consumption went out the door, which I expected, but not to the tune of around 25L/100. The van weighs in at approx. 2.4T. The cruiser is a one owner and has never let me down, but I am surprised as to why it is lacking in power. I thought it would have handled the tow a lot better than it did. Am I asking too much from the old girl or do you think that it may have an issue mechanically? Fuel pump and turbo are close to original (I had them changed out under warranty at around 30,000k) and injectors changed around 150k ago. She is coming up to 400k on the clock. Do you think the overheating, lack of power, excess smoke and fuel consumption could all be inter-related? Is there a turbo specialist that anybody could recommend in the Perth area if you believe it could be a mechanical issue? Any feedback would be appreciated.

Cheers.