I had the same problem with mine too. I was told it would be around $600 to replace the manifold, so I went and purchased a DC sports header. If you don't get it fixed, it will eventually crack to the point of leaking. That won't be a good thing. If you insist on a stock manifold, I would buy a JDM 4-1 header with the heatshields and install that. It will look almost stock and you will pick up some very substantial gains with it.