If you're working for it, your chain isn't sharp.
Really.
Read through this thread, follow the links and load the videos.
http://www.arboristsite.com/chainsaw/198416.htm
It's also why I said to sharpen your chain every time you add gas. It's not excessive. If you're exerting yourself, your chainsaw isn't cutting.
Here is something that is often overlooked. If the sharpness OR angle of the teeth is different on each side, it will cut a curve. I would look to your sharpener. You have good chains but maybe the cutters aren't even left/right.
I used to sharpen my own but I couldn't get the right edge. If I didn't get both sides perfect, it cut a curve. I still do my own touch-ups while cutting but I let my neighbor sharpen. He has a killer sharpener setup with digital angle display.
Practice, same with an axe. Takes time to get it right
Really, chainsaws are for wimps anyway.
http://www.youtube.com/watch?v=Y4lky9VW6tE
But if you are using a chainsaw, it should cut something like this...
http://www.youtube.com/watch?v=kHVufn2nKD0
maybe run premium fuel 
http://www.youtube.com/watch?v=FvAI7-Qa2Io
I guess you have to know that if they make it someone will attach a smallblock chev to it eventually.
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