It probably ain't your fuel filter. Jimnys, especially early ones had a problem with the ECU and crank position sensor. At highish constant speeds the ecu would 'turn the engin off!' and it would only recover as the driver lifted off the peddle and then re-applied presure. The problem was discused on anothe Aussie forum, don't know if it is still running. Mine used to do it but since all the modding it ain't happened for a while. As far as I know Suzuki UK won't admit a problem but on cars still in warranty they will re-set or replace the parts at fault.