What a headache! You need Air, Fuel, and a Spark to run your engine and it seems as though you've checked in most of these areas. However, it idles bad but runs fine once you punch it. It sure sounds like a fuel or air issue to me. I know you say the pressures are good, but what are the pressures at lousy idle and after you punch it?

I find it rather odd that your gas pedal has to travel 2/3 the way to get a response. Is the throttle sensor setup correctly? Didn't the mechanic find that to be odd?

I don't understand changing all the ignition items if there was a good spark. You seemed to have changed everything in the fuel area except the pump itself. Also, in the area of Air, you didn't say whether you checked for a vacuum leak.

Let us know what the outcome is.