The metallic edge mellows after about a year of constant gigging. Did you lower the E string poles on your P-pickup a turn? That should cure the boom.
When they were brand new, I didn't like the amount of high-mid metallic edge of 760M strings but after about two weeks they mellowed substantially though retaining enough to provide nice definition.
I'm glad it didn't take a year for them to start sounding good. Otherwise, I wouldn't have stuck with them for that long, regardless of how much I enjoy how stiff they are.