When did you overclock your card and how did you verify it was stable? If you have so far tried to verify your OC with benchmarks like Unigine Valley, you cannot be sure the OC is stable, whereas games which are more "confusing" to the GPU, will warrant a better stability if used to test. I wouldn't push your card too far. 1343 MHz seems like a great achievement (although I personally would downclock it to 1337MHz for lols) If you really want to bump it up even more, I recommend to increase the clock in increments of 10MHz. I have also found that Unigine Heaven is more likely to reveal an unstable overclock so here is the procedure: run heaven, look for artifacts. If artifacts are seen, you have 2 options, downclock or increase voltage. I personally am not a too big fan of increasing voltages but that's not my decision to make for you. If you are going for the variant without increasing voltages, increase the clock until it's high enough but stable while checking in between every 10Mhz increase if it's still stable. Then play with the clock speeds for a few hours and make sure the games don't crash or artifact. If you are willing to increase voltages which at the same time potentially decreases the lifespan of your card, you should start by finding the maximum clock without increasing voltages as shown above. After that you should continue moving in 10MHz increments but at the same time after any instability increase the voltages by around 10mV. (Voltages are locked or limited to a certain limit on some cards). Continue while carefully monitoring your temperatures. As long as the temperatures of your card don't exceed 85 degrees celcius under benchmark/gaming load, you are fine imo.