First, follow the guidelines Saint19 has given you. He helped me hit 4.1Ghz, so his advice is golden.
After you have set your memory timings correctly, change the multiplier to 20x then up the cpu voltage to 1.325v. If you have good cooler it should have no problems. If you get the blue screen of death (BSOD), you may need a little more cpu voltage, but don't go too high or you'll fry it.
After this, you can either change the NB frequency to 205 to achieve 4.1Ghz or adjust the cpu multiplier to 20.5x. However, increasing the northbridge frequency screws with your RAM and, if you're memory sucks, it won't be able to do anything and may not even start and you'll have to reset your BIOS and start over. At this point you will be at the normal "breaking point" of the processor. I haven't seen many 1090T's over 4.1Ghz, but it is possible if you have a good chip, awesome cooling, and stable RAM.
P.S. don't run Prime95 a lot as this will eventually destroy a cpu. (Word to the wise.)