I'm a little late to the party, but it looks like the community took real good care of you. I;m glad it turned out OK. Remember, Porsche is always going to backup their dealer in the beginning. It's like a knee jerk reaction.
Yes, the MM act make it so no manufacturer can't void a warranty. They do still however have the right to deny an individual warranty claim, as mentioned, if they can prove that a modification or aftermarket part caused that failure.
It is also important to understand that Porsche (all manufacturers really) have the right to limit their warranty. It's a good idea to make yourself aware of the limitations. You can read Porsche's warranty details
here.
At the end of the day, it all comes down to relationship. My dealer knows that I track my car. I don't hide it from them. I have had failures at the track. Just this summer, while at Watkins Glen, my PSM went into failure. This was the third time my PSM failed. When I dropped my car off, my service manager told me, "I don't think we'll be able to warranty this. This was a track failure..." So I prepared for a bill.
When I came back for my car they told me that they had to replace my PSM computer and the steering angle sensor. My sphincter tightened up... I asked, "Ouch, how much do I owe you....." (I was preparing for $2,000). He says to me, "It's covered under warranty...." So I say, "Really, even though I was on the track..." He said, "There is nothing you could have done on or off the track to make this part break like that. This was a defect, and it's a continuation of a persistent problem you've been having. Because this was your third PSM failure we involved Porsche AG on this one. We pulled a full VAL on your car, and yes, we told them you track it. They told us that we need to replace the steering angle sensor and computer at the same time, as a matched set. We didn't do that last time. That's why you're back. Not your fault, not the track's fault...."
Now they could have really jammed me on that one, and they didn't. I respect that. (BTW - I am speaking about Danbury Porsche in CT)