One classical sign of clogged fuel filter is that when you start the car after it has been parked overnight, it will take a longer crank to start and engine will FEEL choked. That is, first two cylinders will start firing, then car's RPM will gradually increase as the third will follow and then eventually the fourth. The car won't start right up on all cylinders when fuel pressure is low. That's just an indicator. If you want to avoid huge service charges then after testing this symptom, pull out your front O2 sensor and clean it with white or apple cider vinegar. Then see if you feel any difference. If still no difference, then check the fuel pressure plus get your CAT converters cleaned. Btw, also make sure that your car runs a thermostat and is not running without it. That will destroy engine's top speed as well.