Losing power?????

[beano]

I have a 1.6 td multivan on a 87 plate!

I had a new exhaust fitted at the weekend and since that has been done my van hit's a flat spot at so many revs!

It is the first time I drove it today since it was fitted and it does it all the way through the gears towards the middle/end of each gear. When it get's to 50 mph it reaches a real flat spot and struggles to get any faster at all.

One of the hoses had fallen off the underside of the turbo box so I replaced that and thought that may be the answer but it is still the same.

This is my first T25 so I am trying to do as much myself as possible.

Does anybody have any ideas what it may be?

Thank you in adavnce.