Depending on your inlet manifold design (i.e. if you have a single throttle plenum) you will get significant differnences in EGT's at idle. This is due to the large difference in AFR's on each cylinder at idle brought about by the each cylinders inlet runner proximity to the throttle body.

As an example on my own car which has a centre feed single throttle plenum I see 300DegC in 1 and 4 headers and 400DegC in headers 2 and 3 at idle.

However this is largey irrelevant as it is your on boost EGT's that are important. Here a correctly designed and mapped engine can see as little as 10DegC between exhaust ports!

With regards to safety limits I personally allow 950DegC in the exhaust ports of the head, and up to 900DegC in the down pipe assuming you are not running with significant exhaust system back pressure. If you are it is possible to see the down pipe temps rise above the head port temps. In this situation you should increase exhaust bore size.

Ideally you should see anything from a 100 - 200DegC drop between head port EGT's and turbo downpipe.