Last March I bought a 2001 S that had 41k miles on it. The clutch was replaced at 32k so there was no way i was going for a clutch/Ims replacement.
Having read in a few places that the IMS was more likely to fail at lower mileages I was plenty paranoid so I sourced an IMS Guardian from Wrighttune for £250.00.
Fitted it myself when I did Oil change a couple of months ago which was pretty straight-forward (and I'm no mechanic though I usually do the routine maintenance stuff).
Like a couple of other people I also found that the oil plug was leaking after fitting. I think my kit was old stock as I didn't get the socket with the cut out they now supply so couldn't torque it up properly. As per instructions I didn't tighten it up too much, so when I found I had the leak I got under and added another 1/4 turn on and that seems to have sorted it.
I initially installed the unit with the audible indicator at the bottom of the center console but found travelling at any speed or with any music playing it could not be heard. Also I had to install the switch with the visual indicator on the drivers side of the dash and found it was totally obscured by my hands and the steering wheel when it's in its's most comfortable position for me. So just yesterday I moved the audible unit into the service-book wallet holder which is much louder, (but still not loud enough really). I also fitted a cheap strip of LED's that I got off fleabay under the speedo/revcounter and wired them in using the auxillary connections on the sender unit. This is far more successful and there is definitely no chance I'll miss it if goes off. (touch wood that it never does).
Must admit that ever since I fitted it I have felt less anxious about the engine letting loose and being left with a beautiful static piece of sculpture. I know this is purely psychological but it's true never-the-less and for that reason alone I would recommend fitting one.
PS.
For all those thinking of purchasing a Boxster .... Do it!........ but don't read anything on-line about IMS failures you will sleep more soundly.