Overclocking 790i isn't quite like overclocking an Intel chipset. It is often best to dial in your FSB and multiplier choice and then work on your memory overclock as you can fine-tune the memory with the dozens of dividers available to you.
The maximum air overclock was one of the highest I've seen for 1.35v. 4617MHz is nothing to snuff at and with more voltage the chip kept climbing.
Dropping down to the 6x multiplier yielded a decent 526FSB. 790i was a great improvement over 780i in regards to FSB but in the grand scheme of things 526FSB isn't too high.
Shifting gears and focusing on the memory, I tightened up the timings to my benching settings of 7-6-5-18-1T and pushed as hard as I could. With 2.2vdimm and 1.5vMCH I was able to get DDR3-1940 to boot and some suicide shots around DDR3-1970. These numbers could easily go up with ~550FSB but it just isn't in the cards without sub-ambient cooling.