You shouldn't have to play with your bus speed, as you have unlocked multipliers. Mine are locked - i'm running 15x multi and 267Mhz FSB. ANd I had to play with the HT and RAM multi's too. You won't need to worry about that so much. If you are happy with 3.8, I would stick there - when I was shooting for 4Ghz, I had to jump my voltage from 1.475 - 1.49625 to reach 4Ghz. And I had to use extra VDDNB too (its CPU-NB volts on my board) I currently run that at 1.31v. In CPUz I hit 1.52V when under load running Prime95. I can't get 4Ghz stable any lower. Oh, I also played around with my LLC settings, my board has different % settings, and I have mine set low - it seems to give minimum Vdroop, and has my Voltage almost match my BIOS setting. JUst be careful playing with it though,, when I had mine on high % settings, it could get pretty wild!. If you play with it, I'd back off your overclock, lower your voltages, THEN play with it, till you get a feel for how the different settings work. You don't want to fry your chip running it near the edge, then having LLC rattle some mental voltage into it. But it's worth having a play with to see if you can get stable at higher frequencies. I know it helped me. Also you could play around with the base clock, try odd settings like 201, 203, 207 etc, sometimes slightly odd frequencies can help with overclocking.
Well thats you had my 2p's (2cents) worth! I'm kinda hoping more experienced OCNers might pitch in.
EDIT - I forgot to mention the throttling - it would bump the voltage down to about 1V, and the multiplier to x4 to reduce the core frequency. Always happened at full load once I hit 55C/56C
EDIT 2 - Have you tried setting the CPU overclocking from auto? what options do you have there? (the top setting in your freq/volt page)Edited by latelesley - 6/28/13 at 2:57pm