There is some Elpida mem out there, that even when modded with the 1500 strap, that seems only stable at 26-26.5 mhs or so
I experienced this with a 480 4gb nitro (not nitro+)
They do 30Mh as well.. (those nitro's)
Got 2 Elpida 4G's, one nitro and one non nitro, the nitro one does 30+ and the non nitro one does 29.5 stable.
But this is with custom timings.
Greetings