The sock filter is inside the fuel tank; you have to remove the fuel tank. It is not a 30 minute thing to do. One trick that is often doen is to blow off the sock or blow the dirt off of the filter formkt he outside rather than trying to remove it and clean it. This is done by:
a) remove the fuel cap and disconnect the fuel line feeding into the fuel pump
b) use some compressed air to blow back into the fuel line from the tank; use a valve on the air supply so that the flow of air can be gradually increased
If the sock is very dirty and plugged up, it will blow off and lay in the tank. On other thing that can happen is that the rubber line that connects the metal fuel line under the car to the metal fuel line out of the tank is rotten. If it gets a crack in it, then it will suck air as well as fuel and give erratic fuel feed. The pressure test above can possibly locate a leak in this short rubber hose, which is on top of the fuel tank under the car, but an inspection of that short rubber hose should be done first to see if is cracked or collapsed.
Please answer some more questions so we can better figure out what is happening; your description of symptoms is confusing, and the focus is on the sock filter since the title of the thread is that the car has problems at above 60 mph. That symptom indicates a problem with fuel flow from the tank at high fuel flows; that is often casued by the fuel pump or a filter being clogged. But, since this is now a problem at all speeds, then it could be something else.
1. How does the car idle now that the problem has showed up again? Is the idle smooth, or is the dile rough and do you have to press the accelerator down to keep the car idling?
2. When you are driving and you have to press the accelerator to keep the car from stalling, do you have to press the accelerator down and hold it down, or do you pump the accelerator multiple times to keep the engine running?