[deliriousga]

It's cheap, low labor diagnostics! "It might be.... We'll replace that part and if that's not it, we'll go to the next part?". I don't blame him for guessing because most people would choke if he said "I'll figure out exactly what it is before I replace anything. It could be one of 8 different things so it will take me about 4-8 hours to figure it out and you will have to pay me for those hours."

If a mechanic ever replaces parts when diagnosing your problems make sure he gives you the part that was taken out just in case he's wrong. Most parts are pretty darn expensive (especially a MAF) and you have a replacement for later when something really happens or you can sell it on eBay.

When you say you're having trouble with the idle stabilizing, are you talking about a steady up and down movement in RPMs or an erratic movement? What is the range in RPM that it fluctuates between? With your first description, and not looking at anything, I'd say vacuum or sensor too.

Next, how much do you want to get into it? You can do most diagnostics yourself, but it can take a good bit of time and you need a few tools. The tools are 1/3 of what you've spent so far so it's worth it if you are interested in learning the inner workings of your Boxster.

Start cheap like Brucelee suggests with the Techron FI cleaner then go from there.