Question: Hi my wordpress admin is acting really slow, is there some diagnostic plugin I can use (like Debug queries on the front end) to see which plugin is slowing down the dashboard?

Answer: 
First i recommend you to use Chrome Ctrl+Shift+j -> Timeline, click record button and refresh admin page and in that timeline you will see what caused the longest load. if HTML then php/sql part is slow, but maybe some javascript causes slow load.

Second - one by one disable plugins and test loading time.
1. you could disable plugins one by one to find the bad guy
2. wp-admin runs a lot of javascript. If you use Firefox I recommend opera or Chrome Which are much better and faster with handling javascript.