look on the block....right where the tranny meets the block. Below the valve cover to the left of the exhaust manifold. You will see a flat spot with a code on it.
If you a have a DX or CX you will have a D15B7 or something.......if you have an SI you will have a D16A6......but an easy way to see if you have an SI or a DX/CX is the intake manifold. If you have a big silver one and 4 injectors....you have an SI.....if you have a big round Black one....and 2 injectors....you have a DX/CX
-Brad