As a number of you suspected, it turned out to be the AOS - much to my HUGE relief!
After writing into the forum and doing some research, I called a second shop that I have dealt with over the years. After hearing my description of what happened, they immediately concluded it was the AOS, they said 90% of the time that is what it is. I took it them, they have repaired it, and I am back on the road with it running perfectly!
Jake, I hope that you are right that the smaller shop simply didn't have the experience.
But after doing the research and calling them back, I asked if it could possibly be anything else and they were adamant that it could not (at which point I had it picked up). However, they were very keen to sell me a Boxter for $18,000, (a car the same year as mine that had had the same "issue" ), they had placed an S engine in it. They would make me a deal on my car for parts – in the neighbourhood of $2,500 – would have been a sweet deal for them, with a $150 replacement part!
I thank you all again for your invaluable input
