After my Honda Civic with 130,000 miles has been running for a while, it loses power. This happens intermittently. Had the timing belt replaced this summer, and had the catalytic converter replaced recently. Problem predates this repair and it still is a problem.
Have you had any Check Engine Lights? If you have not seen one, you still could have a stored error code. Some autoparts stores will read them for free. The code should be in the format P0123. Post the actural error code back here if you find one.
Was the problem after the timing belt replacement? If the timing belt was not done right that could well be the problem.
There is a reason the catalytic converter went bad, if it, indeed, did. Here is a check list for your mechanic. If your mechanic is conscientious, he will carefully follow the check list. http://www.obd-codes.com/p0420
It’s past time to change that fuel filter. A dirty fuel filter will reduce fuel flow to the engine. This can be intermittent. Changing the fuel filter is easy, and cheap (relatively, to the other things).