Hi, I have a 2000 Samurai 1.9 TD and plan to use it in the hills in the Algarve. The problem is that when in convoy, there is a huge amount (clouds) of very fine dust in the air. Will the standard air filter that comes with the car be ok or should I be looking for a more suitable air filter to cope with this problem. Your comments would be much appreciated. Thanks.

Hi, I have a 2000 Samurai 1.9 TD and plan to use it in the hills in the Algarve. The problem is that when in convoy, there is a huge amount (clouds) of very fine dust in the air. Will the standard air filter that comes with the car be ok or should I be looking for a more suitable air filter to cope with this problem. Your comments would be much appreciated. Thanks.

Huge amount (clouds) of very fine dust in the air will get caught in all air filters.  Standard filters plug up and require changing, Other filters plug up and require cleaning, really cheap/poor quality filters allow some of the fine particles to pass through.  It is easier to see that an open filter is getting dirty and needs proper maintenance, than one in a box.  If properly maintained both will do a good job of filtering the intake air.  A poor quality filter is just that, but better than nothing.  The larger area that cfm of air has to get to and pass through a filter the less restrictions it will have.  When a filter is in a box that has an inlet area less than the surface area of the filter it will not be able to pass as much filtered air to the intake as an open air filter of the same size. 
A properly maintained stock filter should allow a stock motor to develop rated hp.  How much you gain with bigger & better filters would need a Dyno to tell.

Thank you for your answer :-) Would fitting a snorkel be of any benefit to the fine dust problem? Thanks again.

Snorkles were developed to work is just such conditions, the theory being the air intake would be above the heaviest dust. I think it would be helpful, especially if the intake were facing rearward during convoy.

Snorkels are actually a great help with dust - as bentparts says - especially when turned backwards.

Thank you for the feedback  Much appreciated.