OK, just to tidy up the loose end. I have now fitted the standard air cleaner box with a new Mann paper element and have done a few varying trips in the car. I have to say I have found no difference in everyday driving. This is not checking the performance on a rolling road or with a stopwatch, however with normal driving and some brisk acceleration subjectively I notice no difference. That said I rarely if ever accelerate hard with my foot flat on the floor, changing up through the gears at maximum revs! So for my laid back driving style no problem.
