EGlsVtak

I bought my eg 4 door with a blown headgasket in the process of taking care of the head gasket i found a z6 head so i figured for 50 bucks why not? The head came off of one of my buddys turbo ex setup and i know for the most part it is good. I got it all together about a week or 2 ago and it runs good ...but at about 4000rpms and up it just starts pouring smoke... well it does it all the time but its not noticeably bad till about then. My boss says its the rings or maybe valve seals and im getting a b series together for it but i was wondering if its worth it to try to put valve seals in it ....if its the rings im not gonna fool with it at all. anybody got any ideas of what it might be?