any ideas on what could be causing the following:
Went out to a short town drive today, Bongo seemed unhappy with occasional rising revs & low power (eg upto 3000rpm @ 25MPH).

Temp seemed stable 70'c/top hose.
Currently running on Biodiesel (20ltrs on Thurs), usually run on Derv/Biodiesel about town & Derv/biodiesel-VegiOil mix for long journeys.
Had the coolant system serviced, pipes & hoses replaced back in March..
Did a DIY OIl/Filter service in April..
will put my overalls on soon to investigate (& change fuel filter) but if any on have any ideas pls post a quick message , thx in advance.

Wayne