Engine Performance problem
2004 Jaguar XK8 V8 Front Wheel Drive Automatic 36,500 miles

I have a late 2004 model XK8 Jaguar that has been fairly reliable until recently. I am hvaing restricted performance when trying to accelerate and then my check engine light will come on. It only happened sporadically at first and now with increasing frequency. The first warning was: Cruiise unavailable. After several times of this happening, it began to also say ASL unavailable. I took it to 2 jag service shops (1 was a dealer). They pulled the codes and all they could tell me was that there were multiple occurrences where 7 out of 8 cylinders had misfired. They reset the TSM and ESM and told me to see if that changed anything. Unfortunately it did not. They also cheked spark plugs and coils and said there was no oil or visible sign of degradation. Any thoughts?