Leak valve xover

Mkay so changed my valve cover today, didn’t replace my gasket cause I just changed it about 3 weeks ago. Everything was going good when I started it, it kinda had a low idle at first then I went to picked up my brother started noticing that my idle is going good. But when I stopped I popped the hood to check and bam it’s smoking from the header.

What’s wrong with it?
Leak on the bottom of my car,

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