Mods/Plugins best performance practices...

[NLP-er]

Hello

I want to ask several questions about best performance practices according to vBulletin mods/plugins:
1. What are best performance practices for vBulletin mods/plugnis?
2. What is the very first hook used during vBulletin request?
3. What is the very first hook used during vBulleting request, where userinfo data is already filled?
4. Does moving code from plugin to php file will improve performance? In what level? I mean move code from plugin to file and in plugin put require to this file.
5. What impact on vBulletin performance has usage of plugin system? I mean if there is lot of plugins which do nothing costly, does costly will be the fact that vBulletin have to handle this plugins? On which level?