fuel problems
 

everytime i turn around i am having to change the fuel filter because the car starts to hesitat when i get to about 65mph, so i change it and then it does fine. what could be the problem. got the car in august, owner said that when they got it it had some problems, but they didnt know what the problem was, so they let it sit for a couple of months w/about 1/4tank of gas in it, could this be the problem could there be some sludge in the tank. if so where can i tank it to get it cleaned out, or will it be better to buy a new tank and put it in. i took it to mazda and they said i needed to replace the shuttervalve, so i replaced that shortly after i got the car and it seemed to do fine after replacing it.

Common probem as our cars get older. You need to get the tank flushed. The S3's have a drain plug, drain the tank. If it is too bad, you may need to pull the tank to get all of the crap out of it. While it is out, pull the fuel pickup out and check the filter sock. It is probably split, that allows all of the debris to get sucked up and plugs the filter.