It's possible that the performance you're seeing is the result of becoming an Ultrapeer. There are almost no differences between 2.7.9 and 2.7.13 (they were primarily installer changes). If you became an Ultrapeer, however, you might see the performance problems you mentioned.

You can tell if you're an Ultrapeer by enabling the connections tab. If it says "Ultrapeer" in the lower left hand corner, then you're an Ultrapeer. You can disable becoming an Ultrapeer in the Tools>>Options window.