I've managed 4.2Ghz with the stock cooler, temps in low 40's C, however it seems slower overclocked than normally, could this mean I need more voltage? Or increase bus speeds?
You're idle is probably in the low 40s but I can guarantee your load isn't unless you're playing with your PC out in the snow. It may seem slower because it is possibly throttling due to heat.
Max temps I've had gaming & synthetic benchmarks its low 60's ( I have my room about 10 degrees C)
The tj max is 83 & its nowhere near that so I'm not sure