following up from my previous post i have been told to remove fuel filter and using compressed air blow back down the pipe from the filter to the tank due to the pump having a filer on it that is known for holding dirt etc causing poor running?
anyone is it advisable ?

Has a P38 got a micro-filter that can be removed from the bottom of the stand pipe?

Personally I'd take the stand pipe out of the tank to remove the filter (if fitted), even if this means having to remove the tank first.

PS. You could always try a "flow test" look in the electrical manual find the power supply for the fuel pump (but don't back feed the BECM), disconnect the fuel pipe, power up the pump independently and check the flow rate.