The wiring harness issue is actually 93 to 95 but the vast majority of them have already been replaced. The 93 to 95s have more torque and noticeable better performance as well as better gas mileage. The 90 to 92 might actually be less trouble overall but have one big problem that would rule them out for me - the ignition control modules are failing. Used ones are very scarce, and expensive, and new ones are unavailable from MB even at a ridiculously lucrative list price. This is taking cars off the road for months at a time. Try a search - there's been some threads on the subject. The later 3.2 cars may be a nuissance at times but at least they can be kept on the road.