what is the usual idle for a 97 camaro z28?

I have a '97 as well and it idles steady at 800RPM.

What transmission?

97 auto here, always just under the 800 mark.

Mines right at 1000 and manual. I've heard there off by about 200.

mine idles around 900rpm and it is a M6.

800 A4

manual, idles at 1000 but I got it checked and it is really at 800, so my tach is of by 200

My M6 idles right around 1000 rpm

usually between 900-1100 on the M6, I'm trying to figure out why the idles varies as much, could be the tach being off though.

Stock programming, fully warmed up:

M6: 800rpm

A4: In neutral 650rpm; In gear: 550RPM

Allow 100-200rpm for stock tachometer error. To get accurate rpm readings, you have to put a scanner on the PCM.

Yep, 1000 on the tach, but my scanner shows 825.

LOL...leave it to GM wizards to get gauges that aren't accurate. Even my speedo is off. Where I live, the cops have this portable trailier that displays your speed via radar. When the radar displays 25mph, my speedo shows 28.
I've chacked the accuracy of the radar using my 2 other cars and both those cars show dead on...so I conclude the GM speedo is off.
One benefit for the tach showing about 200RPM higher is that it gives you that 200RPM buffer to help prevent over-revving, for those without rev limiters.

I'm thinking it's the oppisite. I've heard when revving pretty high that your rpms are higher than actual so if your at about 5800 on your guage, it's really already at about 6000 rpms so in a way that buffer isn't really there. The guage isn't fast enough to climb as fast as it's revving. Please correct me if I'm wrong.

This is true - however I am unsure if its the gauge not being able to read fast enough, or if it is just inaccurate.