Kotlin

There was an interview on everyday astronaut where they talked about it, iirc it's mostly monitoring and measuring sensor equipment they needed for earlier launches.

https://everydayastronaut.com/spacex-raptor-engine-comparison/

"Compared to the original Raptor, Raptor 2 looks borderline incomplete — a large amount of plumbing and sensors have been removed, transitioning the engine from a “Christmas tree” look to a significantly cleaner look. On the original version of Raptor, while SpaceX was learning how to control the engine, a very large amount of development sensors were needed, allowing them to track pressure and temperature throughout Raptor’s plumbing. Additionally, many valves were combined into valve plates, helping further simplify plumbing."

Maybe redundancies later proven unecessary? Idk, not a rocket scientist