Honda Repair: 94 accord power loss, distributor shaft, cat converter

Question
After driving my 94 accord lx with 5 speed for a bout 20  minutes I loose power.  The engine makes kind of a whooping whirling sound.  If I push the clutch in the engine sounds fine.  I have had three mechanics test drive it without finding any problem.  I feel they may have not driven it long enough.  Any help would be appreciated. I have recently changed muffler, cat converter is empty or blown out according to the muffler people.  I have also changed the radiator and half axles and done tune up..wires, plugs, gas filter. Any clues what to do.   Car uses no oil and does not have knocking sound. Dave  

Answer
I would check the transmission to be sure im not exactly sure but the compression on the engine can be low or the clutch can also be slipping hard to tell without driving it, if you haven't checked the distributor shaft I would definately take a look at that.