Start with the obvious. The engine compartment. But the engine is the forest. Now we have to look at the trees that make up the forest, and this is where most stop. But branches make up the trees. When I look under a hood of a car I am tuning, I see per say a distributor. But not just timing. I see initial/ramp/total, phasing, delivery, consistency, etc. If every component (tree in the forest) is broken down by it's branches, then we begin to realize how much time it takes to tune. It's exhausting but fun and very rewarding. Very few will do it anymore, much easier to buy more performance parts.