Whoops, it was Cl20-20-20-40 at 3733, not Cl18. At Cl18 3733 1.28v won't even post, while 1.3v fails AIDA as usual... even Cl20-22-22-42 will fail.
I'm running dual rank, 2x16, so it might be the reason why I can't push the clock higher... For now I'm trying 3600 Cl18-21-21-41, tFAW 16 and tRFC...