i did exactly this to my old 156. Put a cf2 lump in a cf3. the engine is identical and will drop straight in. The only difference is the manifold so you need to keep the manifold from your car and then just plonk the new engine in. Job done.
It is only the manifold and twin cats at the front before the flexi pipe that are different from cf2 and cf3. On the cf3 cars two cats were added to meet the new emissions regs.
You already have these on your car so no need to worry.
Hope this clears things up for you.
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