Holy loose header bolts batman. One bolt was barely hanging on. Two others were loose enough to move with my fingers. A few more needed half a turn to tighten up. I went over all the header bolts 3 times to make sure they were all nice and snug. I will make a note to check them frequently to see if they back out again. It's too late now to start up the car, but tomorrow after I get back from work I'll see if the noise is gone.