So I'm finally going to get my own G35 and had questions/concerns.
what should i look for on used g35s?
like most cars will millage be an issue?
are there certain things that are dead give aways on bad investments?

Yeah, the age of the person who owns it.

Depending on what model and year you are looking at some G35's have an oil consumption problem. There is info on this site about that. I don't remember but I think its Manual transmission pre 05? Anyone? Other than that, 06 and up have the much better projector headlights and newer interior. If you can afford it get an 06 and up.

suggestions on exhaust systems? i want something with a deep voice and loud when accelerating