I have a 2002 Porsche Boxster with 90,000 miles, do I need to change the IMS bearing

Well, that's entirely up to you and your tolerance for risk.... I have a friend who purchased one this age and only 62,000 miles.... He had the bearing changed only to find out that it was in perfect condition..so, it cost him about $4,000 to have a new one installed.when it wasn't necessary... but, he purchased peace of mind... Could be the same in your case OR, you're running the risk of blowing up the entire engine.. you have to choose...

You don't need a Porsche specialist....the IMS issue has been out there everywhere for a long time....and there's NO way to evaluate if you have a problem until your car is opened up...the only thing you can do is either roll the dice and take your chances or go ahead and get the part replaced... that's it...

http://imsretrofit.com/ims-101/

Yes, do it right away!

The single row IMS has a 10% failure rate at 100k miles.