I am trying to find the recommended frequency to change the fuel filter on my 2005 WRX STi. My car currently has about 56k and I am wondering if this should be done at 60k? I am also wondering if there is only ONE filter or two? I have been reading conflicting reports and I believe there is one in the tank and maybe an additional one somewhere else? If there is more than one, do you only have to change the one external to the tank?