The view of Road & Track Magazine. More odd 'stuff' on the IMSB - e.g. "a short run of low capacity bearings, 'some' of which ended up in early 996's."
"The biggest reason for low 996 values is the misconception that the engines have the durability of blown glass. This is one gripe with the 996 that really needs to be addressed. Some early cars featured a weak bearing in the intermediate shaft, known as the IMS. Porsche has used an IMS in its 2.0-liter engines since 1965. The IMS drives the camshafts indirectly off the crankshaft. But even before the introduction of the 996, Porsche had experimented with new bearing designs, and this development resulted in a short run of low-capacity bearings, some of which ended up in early 996's. An IMS bearing failure results in a completely destroyed engine. Luckily, most qualified Porsche shops can perform a pre-purchase inspection and identify bearings that have been upgraded or may need to be replaced.
As terrible as a blown engine is, enthusiasts have made it seem like every 996 came with a defective engine. Further fanning the flames, Porsche's handling of the problem was a PR disaster. But the reality is that the majority of the engines are fine. "Engine failures in [engine model] M96 in actual real numbers range from one to five percent," Brownell says. "It's more than there really should be, but it's not quite as dire a situation as the Internet would have you believe." What's more, the problem can be corrected by a $400-$700 upgrade."