[davidcroft]

The issue is specifically with the titanium intake valves. I saw an 06 that had been rocking a cam for a while (and not a good spec'd cam) and he pulled the heads to get them ported and get a good spec'd cam for his motor. The intake valves had so much play in the head it was ridic. But yes they call it valve stem guide wear and I'm not sure in GM engineers know what's causing this issue, or if they're even admitting it's an issue. I do know that this issue has arisen in the past couple of years and the LS7 has been out since about Feb of '06. Like all issues it won't affect every car. Like hognutz said, you can pull the rocker cover and see if they're making proper contact.

I do know that if you're thinking about modding a Z/28, you can be willing to bet GM won't be as mod friendly on the service side. Those LS7s are expensive and motor claims will probably trigger a field engineer to inspect.