nononononono
its not ON the header...its on the BLOCK (that big aluminum thing that has all the engine stuff inside) to the left of the header. here... looks like this but B18B instead:
maybe this will be easier...look at the engine from the front of the car. see the top? thats the valve cover. now, go to the very left edge of it. youre at the corner now right? go down maybe 12 inches. you'll see a square with the numbers stamped big.