I've had a '99 STS for about 6 months now and it runs great most of the time. However, it has quite the thirst for dex-cool and is running through the stuff fairly quickly. The car runs fine at speed but if its been running for a while, the temp creeps toward the red but has yet to actually hit it. Once the car is moving again it cools back down and is fine again. I previously had a '99 SLS and loved the car aside from the head gasket issues and kind of know what to expect there, so I'm skeptical of the STS's issue being in the head gaskets. The symptoms have pointed to the idea that it could be an intake manifold gasket going bad and so I am wondering (and hoping) if that seems more likely than a head gasket issue. Any advice would be greatly appreciated.