Question about a researchable module on a plane

This is the P-51D-30.

Why would this module make the speed go DOWN??

This is not logical…

Is this just a display bug or is this really taken into account when researching?

  • E.

From what I’ve checked it’s probably a bug because I don’t have it right now.

Still there for me… Same P-51 version? The P-51D-30?

Yeah it’s P-51D-30 one at BR 5.0.