recently my superb is lossing its speed especially on tackling hills, someone has said it could possibly be air flow meter

How could I test the air flow meter

Also i have been running on occassions on bio-derv

car has been recently serviced

200k? Running out of puff maybe?

If its on its original MAF then thats a good place to start for sure.

Its a bit naughty running these PD engines on Bio though...