Hooks not working iff im using @ob_start()

Could you provide us with an example code?

Why are you bothering with compressing HTML? With modern internet you will not find it worth your while, as long as you have gzip enabled on your server for HTML.

Have you placed exit; after all your redirect(); functions? That's the only way to get rid of "Cannot modify header information"*.

If it's not your redirect() functions creating problems, you may have whitespace in your files. UTF-8 BOM etc in your files.
https://stackoverflow.com/a/8028987

* The easy way at least, as you need to stop it rendering HTML or other content that sends headers.