I given up trying to fix mine - im taking it to Ford Dealer on Thursday and let them have a look. Ive done leads, plugs, coilpack/inginition thing, inlet manifold gasket, ISC gasket and clean, new cat. Slighlty better but still rough. I let you all know what they come up with.

I took mine to my local dealer a few months back in the same hope. When i returned to pick it up, they told me they couldnt even feel a miss at all. Jumped in and started it and its the same as ever. When the mechanic stood there with me saying he still couldnt feel a miss, i got in and drove away, and havent been back since.

well after checkin everything electrical and all sensors dad and i came to the conclusion that it was a vacuum leak

so yesterday i started the car and listened for anythin, and i could hear sucking
so i got some carby cleaner out and started sprayin until revs lifted or i heard it being sucked in

then once i heard that i looked to where it was comin from and noticed a huge split in the gasket so now im putti na new one on

Just heard back from Ford dealership re my lumpy idle. THey have regapped the plugs and check the engine management system (ie they could not find the problem - only $95 too.
THey say it will always idle like this due to the lumpy xr6 cam - s**t - factory cam is certainly not lumpy. Sounds like they have no idea!

I am going to replace the rubber o-rings on all injectors and see if this helps.

Next option is to sell the car - fq3w9rqwuf0ck.