Loss of power at highway speeds

[WMUGrandAM]

When i first got my car, it had all sorts of power when it got up to about 55 or 60 mph, but over the last few months that power has been disappearing rapidly. I've replaced the air filter, and no change there. Also, the engine is running just as smooth as it always had. Just wondering what could be the cause of this power loss. I've also been using fuel system cleaner regularly, so i don't think that would be the cause of it. Any Input? Fuel filter? One of the the sensors?

[1fatcat]

Fuel filters should be replaced every 30,000 miles, so if you haven't done yours in a while then try that first...it probably is overdue for it anyways.

[rixGAphx]

A plugged cat is a very strong candidate as the problem source.

-Rick