Not sure of this but. Looking at the exhaust manifold under the hood.I see a crack thru vents - runs vertically. Car runs fine. Just seems a bit noiser sometimes. Especially on cold starts. Do I need to replace this or what problems will it cause me in the future. Car really runs just fine.I hope I am decribing the correct part! Thanks!
Take the heat shield off and verify the crack. Use a penetrant on the shield bolts (I like PB Blaster) to prevent them from breaking.
If the manifold is cracked, it must be replaced. A leaking manifold can damage wiring, sensors or even the head.
Soak the manifold bolts for 24 hours with PB Blaster (it is a spray can) then remove them. Get some new manifold bolts/studs and put a dab of anti-sieze on each bolt before installing them in the head.