Ford Repair: 2.0L engine with rough idling, mazda protege5, mass airflow sensor

Question
I was hoping that you could help me with this because there is no mazda expert available to help and I know that Mazda and ford are very similar.  I have an 02 Mazda protege5 (2.0L mitek engine is similar to ford focus') with 80k on it and it is idling rough. There is no problem with throttle response while driving but there is a problem when the car is either in neutral or the clutch is in and usually happens when I'm slowing down, the rpm drop from .5 to almost 0 until the car just about dies then they rise just enough to keep the car alive. If I hit the gas, the rpms go right up and once I stop or idle, it idles rough. I doesn't always do it but it is becoming a lot more frequent (every other time the car is driven) and usually occurs when the car has been driven for a little while.  The check engine light does NOT come on. I have replaced the spark plugs, wiring, coil packs, mass airflow sensor, cleaned out the idle air control valve and intake system, as well as giving it a gas treatment. I also know there are no leaks in the vacuum system.  I even took it to Mazda and they said that they couldn't figure it out unless the check engine light was on and then they stuck us with a $250 bill for replacing the wiring, plugs and coil packs, then they put 60 miles on it over two days and said that it didn't happen for them. We didn't even get it all the way home and it happened to us. My last resort is to replace the idle air control valve but I don't want to do that unless I talk to an auto expert first. Just let me know what else you think it could be so I can check that as well.  Thanks for your time and help.

Answer
did u replace teh fuel filter , sounds like a problem that the focus had with fuel pumps , i would check out the fuel system ..... which ever dealer told u that ,i wouldnever go back to them  because that is false ... appernently they dont have any good auto techs