EGR manifold paassage discolored .

[KWIKR 1]

I have a painted manifold on a newly rebuilt engine . I notice the maniflod EGR passage just under the EGR valve is discoloured . I sort of shinny gold/copper colour . Does this mean anything ? such as the EGR not functioning right . It's a brand new GM EGR valve .I'm trying to track down a high rpm knock and wondering if it could be related to the EGR . I've tested the EGR by pressing on diaphram ,and idle does stumble when this is done . Thanks.

 

[sixgun86gn]

my old intake did the same thing.It should be nothing but heat discoloration.It never affected my performance.

 

[KWIKR 1]

Thanks , I was hoping that's what it was .