[thstone]

At 58K miles, you seem to be past the early failure zone. From here on out, any of 22 known failures can happen within your engine. This is why Porsche and your indy shop say to skip the IMSB upgrade. I'd drive it until it blows up and use the time to plan and save for the rebuild when it does.

112,000 miles 996 (still running strong)
126,000 miles silver Boxster (engine still running strong)
204,000 miles black Boxster (engine finally failed, cause unknown and don't care)