So I took the car to Ken at Vintage BMW racing to look at the header and help me diagnose it. We determined it was the number 4 cylinder tube near mounting plate. So on my next day off I removed the header and took it to the muffler shop that’s been doing the work on the car lately OC Muffler I Costa Mesa.
Here is the crack.
Once it was welded and patched the header went back in a hell of a lot easier than it came out and wham! No more noise!! Excellent result! Cost me about $50 for the repair including a new exhaust manifold gasket. This is a temporary fix though. The plan will be to replace the header. This will probably be the Ireland Engineering Alpina style header which is about $500 plus install and any pipe work that may need to be done by the muffler shop.