`I've got a GM Performance parts crate engine (290hp/350) that has 4k
mniles on it an edlebrock 600cfm and Performer intake. Lately I've been
getting smoke from the exhause (new headers and split exhaust)
Especially when it's in Drive. Blue smoke meaning oil I think. Is there a
way to see if it's the valve seats before I go through the warranty hassle
with Chevy?

If it smokes continuous it might be rings. If it goes away and comes back at start up its seals. You can't check the seals without pulling the valve springs. And you should not be having any of those problems with that many miles unless you run it HOT and burned the rings.

it Makes me sad..but should be a warranty issue....I am curious if anyone
has used a GM Performance Parts Crate motor and had a warranty
repair...if so, was it painful or painless....