All I am saying is that a fuel filter is there to FILTER the fuel. Any dirt in the tank or fuel will be taken out by the filter. Filling up out of a can or just the accumulation of dirt over time will be in the filter.
Its just something to try who knows how old the car is and whether it has had the filter changed. It may be that the car is 6 years old and has never had a filter change, unlikely but possible. The simptoms he has given could indicate a blockage in the fuel filter.
Monster, if you have a mate with an IS try swapping the fuel pump relay. Sometimes they can play up and cause all sorts of problems.