Lots of possibilities here - can you post your full RAM timings and voltages? And also any error messages when you crash?

VTT will play a big part in stability with 4 DIMMs with the CPU overclocked - have you tried up to 1.20 V ?

You will also need to try CAS 9 (i.e 9-11-9-28) and 2T if running 4 DIMMs.

tRFC at 145 may be too tight for 16 GB capacity - try increasing to 200 and test up to 300.

I have 4 x G.Skill PSC sticks and I did manage to get them stable at 2200 MHz on an ASRock Z77 mobo using the memory strap and then pushed up to 2250 MHz by increasing BCLK.

There's no doubt that 4 DIMMs put a lot more strain on the IMC at high speeds, especially when the CPU is overclocked.

Increasing VCCSA *may* help, you could try ~1.10 V but you shouldn't need more than 1.20 V.

You also need to consider that you could be hitting the limitation of one or more of your RAM sticks.

Test each RAM stick's limits individually in slot 2, then put your best 2 sticks in slots 1 & 3, and the other two in slots 2 & 4).