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."