Van Aaken box Help please

[c.morewood]

I wonder if theres anyone using the forum who could test my Van Aaken box. I've been running the Hdi with it for the past 10 or 11 years and it really gives a bit of power low down outside the normal Xantia powerband. But now and for the past couple of months I've been down a bit on low down power and mpg. Its noticeable as I'm having to change down going up hills where previously she would have gone up with ease... just like the box isn't working.
As soon as you get into the normal powerband she's away.
I have checked for an exhaust leak, that I think has caused similar symtoms before,can't see anything or hear anthing unusual.
Just before all this started I was refuelling and went to start up afterwards and she wouldn't start.. turned over but no go, so thinking it was the lift pump again I called the AA man. He couldn't find anything wrong and started her with some easy start.. she hasn't missed a beat since .. apart from being down on power.. do you think an ecu reset would help? Thats my next port of call, then its the box.
Thanks,
Chris