Kobelco sk120-3 LC weak track and boom up

Hello, I have a Mark 3 kobelco 120lc that has recently had the pumps rebuilt and runs great but has no power tracking (high low speed works) and a very slow boom up.I recently replaced one of the final drives (broke) and it didn't change the track power. I replaced the hydraulic filters and fluid. Also the pump whine is louder than it should be I think, the boom also drifts down when left In the air even running.
Thoughts on where to start?
Thanks

Kobelco sk120-3 LC weak track and boom up