Having recently been on the search for a Boxster S, like many others before the IMS was a concern. However it was less so for the pros. I provide this link to one of Pedro’s videos discussion the IMS and also Road & Race UK. Take it for what its worth in gaining more info.
One of the overlook things that I continually found was the focus on IMS was what
Gelbster has noted several times along with Flat6. There are many causes for an engine failure other than the IMS. My you enjoy your ride with data that works for you.
Pedro's
https://www.youtube.com/watch?v=hzUq2DFpeKw
R&R
https://www.youtube.com/watch?v=8lv4V232Bx8&list=PLNKrPMJBU7WhWJWDcSdS4BFK2d182oHPV&index=23
Video looking at several IMS kits.
https://www.youtube.com/watch?v=IxdvSq_byZw&list=PLiya6G1pHhIYyzhlVzS_LwoIovrlv6_lv&index=16