here goes some visuals if you are the DIY kinda guy

http://www.pelicanparts.com/techarticles/Boxster_Tech/28-FUEL-Throttle_Body_Cleaning_-_Boots/28-FUEL-Throttle_Body_Cleaning_-_Boots.htm

I had the same issues, my solution was a new MAF, and new O2 sensors. Unfortunately, this can be expensive since the sensors are like 60 bux or something like that.

I did clean the throttle body and intake tube about 10 months ago, but could take a look at it again. I actually have a spare throttle (an entire intake manifold) that I could use as well. I don't think that will be the problem though as its not just a rough idle, but more of a low air speed stutter (take a slow corner and when you accelerate out of it, then engine will stutter).

I've ordered a new MAF as this is something that I have not changed since getting the car two years ago and have no idea just how old it could be. After hearing the good reviews of ebay sensors, I have purchased a $89 one from the same seller that others here have used.

I might also invest in a second wideband sensor and also re-calibrate my other wideband (have one on the right bank and the stock sensor on the left) to ensure they are reading correctly. Innovate LC-1's are similar in price to the stock oxygen sensors and can do oh-so-much-more!

Hopefully then, she will be as good as new!
Sam