Can we restore the performance of the server by deleting work items?

We have an RTC server instance, which has degraded performance (across functions and not just limited to loading of plans) over a period of time. Can we improve performance of the server by deleting unwanted work items. While I understand server configuration/tuning has a direct relation on the server performance, but given our limitations with server / hardware capacity, deleting work items is a viable option or not? Does the number work items (plan work items vs. execution tasks) really contribute to the performance of the server.