A little late to the game here and you have prob fixed this but thought i would add my 2 cents....
I would bet your timing is off, especially if you have tried to adjust the idle screw on the motor. Doing this even a little bit will change the timing and thus cause the motor not to idel or idle rough depending on how far off it is but still allow it to run wot. It will also make it hard to start. If you have a timing gun you can check and adjust this yourself if not take it in.
So did you get it fixed yet? If so what was it?