FWIW, I have the CarMax Maxcare warranty on my Boxster S. It's already paid for itself in the 2 years I've had the car. CV boots on both sides, a bad camshaft position sensor, front motor mount, and a couple other things that I can't recall at the moment. What I like about it is:
1) You have the option of bringing the car back to CarMax for repairs, for a $50 deductible each time, or taking it to the shop of your choice for a $75 deductible. (Which means that every time I need a repair, I go straight to the local Porsche dealership. No way the CarMax service techs are EVER going to touch my car.)
2) You can cancel the Maxcare warranty at any time and get a refund of the amount you paid for it, prorated for the greater of the miles traveled or the time left on the warranty. (Did that with a previous CarMax car that I decided to sell before the warranty was up.)
I'm happy to say that I can't answer your question of whether Maxcare would warranty an IMS failure. I know that my service writer at the dealership would fight for me to get them to do so, but frankly I hope I never find out. (And he is actually a big supporter of HPDE's, performing a free tech inspection for me before every event. It helps that the dealership sponsors the events through our local PCA chapter.)
