I'm glad this topic has been raised, I too am suffering from the same symptoms, being after about 3.5-4k revs, the engine just hits a flat spot, it will go through the rest of the range but runs like a slag!
I have this morning taken off the connector block powering the MAF, and I believe you lot have helped me no end. Without the MAF connected the car runs like a dream, right round to 7 with no problems! Now, I don't want to keep running the car without the MAF connected, so just how easy are they to clean, are more to the point, what are the chances that cleaning will help? Or is it definately a new purchase required!?