Alright I got the multiplier to go to 180x21 stable, when I moved it up to 190x21 Windows wouldn't boot.
 
I took into account the bclock holes the guide referred to, so I simply increased it to 200x21 and to see where it took me. When I tried that it gave me the blue screen.
 
Ideas?
 
After some more option tweaking, yeah Windows simply won't boot. Windows 7 gets to the point where it does that little spiral as it starts and freezes either as it starts or a second into it.

You followed the guide from the beginning right?  The part where it says to set the multi to 15 and start cranking the bclock in 10mhz steps and as needed the vtt to find your max bclock freq?  Just asking because it's sounding like you left the multi at 21 which defeats the purpose of the guide.

Oh wow, I may have overlooked the 15 multipler, that I did not do. I kept the multiplier at 21.
 
I was increasing the frequency number by ten each time lol, so I started it at like 150, then went to 160, then 170, 180, and finally 190.
 
When I hit 190 I started having trouble with booting (VTT increase fixed that). I jumped the VTT to 3.25 and I'm at 21 x 200, tried stability testing it and I failed again.
 
 
 

20x200 is already pretty respectable if you want to stop there. If you'd like to keep pushing your BCLK, then continue with a 15 multiplier as you said, and keep tweaking your voltages.
 
To confirm stability when you eventually get there, run IBT on Maximum for at least 20 passes, and throw Prime 95 on later as a separate test overnight.

He means mhz as in the BCLK mhz. Bump that up by 10, and then test. It'll increase by 15 at a time for your real clock speed since you're using a 15x multiplier.

It may be because your BCLK is SUPER high that it becomes unstable, no matter what the voltage. Most people don't go over 200 BCLK, but you can try fooling around in the lower 200 range.

Doesn't seem like my system wants to go past 4.0 GHz, I guess if I wanted to go higher than 4.0 GHz I would need to tweak some of the other settings but I guess 4.0 GHz with 16GB of RAM is my maximum!
 
Well hopefully I come across some information that'll allow me to push my overclock past 4.0 GHz. I appreciate all the help guys, I can't thank you guys enough!

Very nice! Glad to see that through 3 pages of work, you've finally come this far!
 
It's not a solid 4.2 because the BCLK fluctuates by one or two just naturally. No idea why. Bring your DRAM's voltage down to 1.5V, since that's what it's rated for. Like you said, Vcore and VTT are a little high, but if they're what you need to be stable, then keep em there.

Hey progress cool   So just a few observations.  First, what temps are you getting at that speed and voltage with HT on?  That's gotta be putting out some brutal heat.  Your vcore is fine considering you're on water for that high of an OC, but your vtt seems too high.  Oh and yes you should manually set your RAM voltage to the 1.5v it's rated for.
 
As far as the guide, I think you're misunderstanding how it works.  So I'll write a quick summary so you understand the flow.
 
Step 1, isolate bclock from memory and cpu to find highest stable bclock.  Setting the multi to 15 take the cpu out of the equation because it's going to run very slow, even at 200 bclock that's 3ghz and should not be a problem.  Setting the RAM ratio to 6 temporarily underclocks your RAM as well, taking it out of the equation.  Then you bump up in 10mhz increments until you can't stay stable anymore even with VTT increases then go back to the stable one and try 2Mhz increases.  Now you know the highest potential bclock you can use
 
Step 2 checks for your highest bclock with memory in play.  If you're shooting for 200 bclock and using 1600mhz memory, you want to use a ratio that gets you within 10% on either side according the the guide.  In this case that's ratio 8 (vs. 12 on a stock 860), leave the cpu at 15 to keep it out of the equation.  Start over at 150Mhz bclock but leave vtt where it was and repeat step one as high as you can go increasing vtt again as needed. Then you should run 1+ passes of memtest as well as burn test to check for stability.
 
Step 3 put the cpu overclock into play.  Don't touch the RAM settings but you might have to touch vtt later.  Start by setting multi to 20 or 21 depending on if you want to hit 4.0 or 4.2 assuming you can hit 200 bclock still.  Set the bclock to 150, and again repeat step 1, but increase vcore voltage as needed this time, and very probably vtt once/if you get to 3.8+
 
now you theoretically have a stable overclock.  That's a very simplified summary of the guide so make sure to re-read it for details and "why" type info.  Hopefully laying it out like this will help you understand why I'm saying to work through the guide.  Yeah it can be a bit tedious, but then, you've been trying this for how many weeks with no success already? 

I'm around the 65-70 range, 71 was the max temp I saw (using Prime 95). I need a day to day overclock, meaning something I can use everyday without worries of things breaking down.
 
I'm not sure if I should go higher (past 4.2GHz) considering I will be using this thing everyday.
 
What do you guys think? I also woke up early (don't know why, body wanted to wake up lol) and I decided to try a lower VTT and V-Core. I lowered the V-core to 3.5v and VTT to 1.425, I ran Prime 95 for 15 minutes and did three cycles with Intel Burn Test and it passed. 
 
I will try for a 1.4 VTT today.

1.35v I meant to say lol.

You sure it doesn't say something like 3995Mhz or something like that?  Due to fluctuations it may not show up as exactly 4000 but it shouldn't be 3900 either.  I don't know about that post code, the closest info I could find was that it used to be for an error detecting a floppy drive, but the P55 doesn't even have a controller for that so it can't be that.  Based on your voltages I'm thinking maybe more vcore.  I know you lowered it from 1.4, did you have the 6F at 1.4v? 
 
Also, I can't remember the BIOS setting (and can't check right now) but on the page with the voltage adjustments, just above the voltage adjustment is setting that the description says is used for bclock of 200Mhz and above.  I believe it's the clockgen switch mode you listed above and it should be set to ON actually.  Don't be alarmed, but whenever you cold boot (from power off or changing BIOS settings that cause a shutdown/restart) the computer will come on briefly, shut off, then come on again a few seconds later.  This is the BIOS doing some kind of stability check the way I understand it, and might help the 6F issue (it's a wild guess but it couldn't hurt to try it).

Alright well been offline for awhile since I was sleeving but I was having trouble with my 20 x 200 overclock (6F) so I tried 21 x 191 (just above 4.0) and I don't get 6F anymore although my PC is now randomly rebooting itself.
 
I had the computer on this morning, went to work, came back and boom the login screen. I logged in, did some stuff (everything ran fine with no problems), finished up and went to the store, came back and boom login. I again logged in, went to take a shower, came back; you get the idea.
 
I'll try the clockgen switch mode and see if that helps.