P3 Plugin assistance

When I was starting with WPMU DEV I found a recommendation to upload a plugin to test my plugin performances, which I did (it is the P3 Plugin). When I ran the software on my http://www.energy-balance.com.au website I noticed that a plugin that had I deleted a LONG time ago was still slowing down my website speed. I asked GoDaddy if they could help me to work out why this was occurring, but as it was a WP backend issue they would not help me.

I originally joined WPMUDEV so Hummingbird could increase the site speed (it was taking 8-10 seconds to load each page), but I am not seeing much of an increase in the load speed times. I figure that there still must be elements of the old plugin stored somewhere in the coding of my website and I do not have a clue how to get rid of it.

When I try to run the P3 plugin again I just get this message: Fatal error: Call to a member function display() on a non-object in /home/content/p3pnexwpnas13_data03/53/3042653/html/wp-content/plugins/p3-profiler/templates/list-scans.php on line 8

Is this something that you guys would look at for me?