It's not the pcie slot, if you overclock too much the card, like the core or memory that could happen easily.
It's a low end card, i don't think it has much room to oc.
The card comes listed as overclocked. Can't seem to find what the default setting is on speed and such. I've done burn in test and such with programs that come with card. Temp doesn't raise much with the double fans on the card.