If memory serves me correctly the 1090T and the 1100T were both good overclockers.
Werd. 4 GHz was usually a decent target goal that most could obtain. Some more 'golden' type of chips could hit 4.1/4.2 as 24/7 clocks. The only depressing thing about overclocking those was that the IMC can't handle very high RAM frequencies.
You'll get a decent performance boost when overclocking the NB/CPU value as well (2600/2800 MHz).