X5 multiple misfire??? Help

I have a BMW x5 3.0; 2 different diagnosis: 1) bad coils and spark plugs, 2) #6 cynlinder misfire-compression and plugs good; intermittent loss of signal to #6 fuel injector. Faulty PCM. See dealer for computer and reprogramming. Help? Anybody seen this type of problem? I replaced all 6 spark plugs today. it ran pretty smooth, slight rough idle when stopped. I drove it about 7 miles. I went in the store; came out; drastic rough idle again. Drove home, barely. It barely accelerated, ran rough.