Rep Power: 0

My 02 civic Si Veloz very suddenly lost power. The cold air intake is louder than usual, so loud that I thought the exhaust pipe was the issue. I can only accelerate to 3300 rpms before the engine begins to decelerate(even with the gas pedal to the floor). I have to downshift(sometimes down to 3rd or 2nd gear) to get up a hill. The exhaust note at idle speed sounds like the grunt of a muscle-car, not smooth like it once was. I don't know the engine code, but it indicates there's a problem with the MAP sensor. It and the idle sensor were replaced to no avail. That code went away, then came back. Mechanic says the cat converter is okay. The transmission, clutch, timing belt and fuel pump were replaced 4-5 yrs ago. Sometimes when I drive with a cold engine, all symptoms disappear and it runs smooth as silk(only for a minute or so). Any idea what the problem is?

 
Rep Power: 312

You need to clean the throttle body. The intake valve is probably sticking on crap and not flapping properly. Among other dirty things.

 
Rep Power: 0

Catalytic converter is clogged.

 
Rep Power: 0

The throttle body has been cleaned. When I disconnect the idle sensor it runs better, but jerky enough to induce whiplash.