[thstone]

I think what you're hearing is advice to keep the engine above 3000rpm to avoid IMS bearing problems. The IMS bearing is rumored to fail earlier if the engine is driven at low rpm (<3000rpm) on a continual basis (supposedly especially bad is lugging the engine at low rpm).

I have no idea if this bit of Boxster-lore has any real validity but if you do a search on the IMS bearing I am sure that you can read all about it.