One of the biggest mistakes most people make when adjusting blade tension is that they ignore the lower guides. That said, when I adjust the tension I insert a slip of paper (fold it once or twice) or a matchbook cover between the blade and the guide. You can also use feeler gauges if you have them. Adjust both the upper AND lower guides (below the table) to the same settings.
Also, the real blade tension must be adjusted using the tensioning knob that's usually located on the top of the saw. For that setting, I usually make it fairly tight, but with some minimal lateral movement.
Lastly, don't forget to adjust the tracking of the blade. If all of those settings have been made the saw should perform much better.