How can you improve upload speed. I have it set to unlimmted but im always stuck at around 90-100 kb

Your throttling could be from any number of sources - including the 90-100 kb/s being the download speed of whomever is leeching from you.

But that said, also look throughout the settings in your client - sometimes there are multiple ways to throttle upload speeds (including limiting the number of connections) that all have to be removed to enjoy FULL upload capabilities!