I have a Macbook Air, and I got it in 2012. Now it is getting slower and sluggish especially after I updating to OS X Yosemite. I knew there are many Mac cleaning tools and some of them are not free. MY question is : Does these cleaner really work? Will they boost my Mac speed?This forum gets some requests of Apple. And there are some experts here. Myself, I have no had a Apple desktop for a long time. But the Apple support community is very active. Here is a post I just found that sounds like your problem
Yosemite slow on Macbook Air
Take a look and see.
In general all PC "cleaning" tools are GARBAGE...i'd STAY away.I'd suggest to GET speed back you could try saving all data to an external drive and performing a  clean install of the OS. If its still slow after this then, you would need a hardware upgrade to increase speed if it even supports an upgrade. If its internet SPEEDS then you will need a faster internet connection or stop others from hogging bandwidth choking your system off.

Most systems run better after a fresh install of an OS that is then updated to fullest security updates. However I am not a Mac guy and so you might find that your computer is just too weak of processing power to run the OS of choice at a speed that you desire. If it were a Windows based system I would be of more help on this subject. 

Cleaning Tools generally dont work out so well. Most dont help and sometimes make the problem worse. The cleanest you can be is a clean fresh build of the OS.