Yanmar excavator slow swing motor.

Hi everyone, I have a Yanmar VIO55-5 with a slow swing motor, and the blade also has a noticeable delay. Originally, both the blade and the swing were very weak and slow. I replaced the gear pump, which fixed the blade's lack of power and improved the swing performance, but the swing is still slower than it should be. Here are the pressure readings: Pilot pressure: 550 psi Blade pressure: 3,550 psi Swing motor pressure: 2,900–3,000 psi One thing I've noticed is that when I start swinging, it begins fairly fast but then slows down. However, if I operate the dipper (arm) at the same time, the swing speeds up noticeably. Has anyone experienced this before or have any ideas what could be causing it? Any help or suggestions would be greatly appreciated. Thanks!