Whats the mileage on the td?

It could be the turbo thats gone. The 1.8D i had before my TD engine swap struggled to get up to those speeds and had crap mpg so sounds like the turbo could knackered. Keep an eye on the oil level and exhaust smoke colour for any difference. With a wrecked turbo usually theres plenty of oil loss. Try taking off the plastic intake into the turbo, 2 10mm bolts and try moving the turbo blades side to side to check for bearing play... The less play the better.

Alternativly check the connections on the fuel pump. And theres is a small rubber pipe that goes from the turbo to the fuel pump, which when on boost ups the fuelling for the engine. so check that its ok. It could explain lack of performance