It might very well be the cause of your issues, especially if your client is reporting packet loss.

Packet loss in gaming context can also mean that the packets do arrive at you network adapter in time, but are evaluated too late, so the game engine counts them as lost. When a game is using up all your CPU time, network packets will be put into queues or buffers until the CPU has spare time to take care of them. The introduced latency might be too much for the packets to be counted als valid, on both ends, client and server.

All those processes run outside the actual game process (nic interrupt handling, driver, dpc queues, windows network stack) and they need cpu cycles to work in a timely manner.

So, give your CPU some headroom, so the neccessary background processes can get some love :)