PokerAce Hud could lag displaying stats but it should not lag your poker client or PokerStars although I will not say that its impossible (if things are simply not configured properly).
Please read through the
Tutorial: Troubleshooting Performance Issues which should ensure that PokerAce Hud and PT2 are running at peak efficiency.
If you are still noticing this lag, enable logging, open PokerStars, play 30+ hands on a 'single' table then send me the PAHud.log file via the
Support system so that I can review your configurations and troubleshoot the issue.
I will say that PokerStars is one of the smoothest sites that PokerAce Hud supports and we have had very few (if any) problems on this site, especially lag.
Best regards,
Derek