DefaultCompletionItemManager Linq Code not performant

[SmikeSix]

https://github.com/microsoft/vs-editor-api/blob/61ca43c05f2254b80e87dccaf029acec3f25feb3/src/Editor/Language/Impl/Language/AsyncCompletion/DefaultCompletionItemManager.cs

Hi im writing a voice plugin for intellisense and used this as reference. The linq code for the filters seems to performs really badly. Just stepped through it and rewrote it in normal c#. 10x performance increase. not sure why though