Folks,
I've been playing all night modding an ASUS GTX 660 and I don't have good news. It seems like the GK106 GPU (or this specific card) has a hard limit of 115% on the Power Target, which is 115x1.15 = 132.5 W exactly. Now it makes sense why only 110% is the maximum allowed by default. I tried everything with BIOSes from multiple vendors, etc... believe me. Details to follow later on. Would be nice to have somebody else with a GTX660 to confirm my findings.