Every Crossfire I have every heard run has what I would call a extremely loud valve train noise at idle. The initial cold startup is usually when it is the most noticeable, then is only noticeable at idle if you are listening to it and know what your are listening for. By the way some people can't hear it at idle my wife and kids say the can't hear anything. I suspect it is either a frequency thing or knowledge of what you are listening for or a combination of both. If the noise is only a slight ticking noise it's normal and nothing I believe you need to worry about but if it sounds like loud lifter noise as they are being mushroomed out then you have a issue that needs to be addresses. I think a lot of folks on this forum hear a noise then do a search and find all the symptoms of floating lifers and assume that there is an issue with their car when in fact it is just an extremely noisy engine.