I have gone thru all the steps for optimizing window 10 to run smooth with sonar and gone thru my settings in EWQL,BFD3 and Omnisphere. Working on a pc with 18gb ram.Audio interface is Focusrite Scarlett 18i20. I just cant get the existing project to run without stuttering and then dropping out. Any advice on what else to try to find a solution to this problem?

What sample rate, sample size and bit depth are you using?  What other values have you tried?

Bit depth is 24. I have tried both 44100 and 4800 sample rate. I have tried 128,256,512 and 1024 buffer size on my asio control panel

Forgive me if I ask you to try things you have already tried, but here goes....

Note: on my machine with a Focusrite Scarlett 2i2 I get best results when set to at 44100, 24bit, 256 samples

Latest drivers (graphics and Focusrite?) 
Fully patched Windows
Core Parking off?
On Board sound disabled?
Disable speed step?
Plug Focusrite directly into PC USB, not via USB Hub?
Disable power management on Root hubs?

Try renaming (don't delete) your AUD.ini file and then let Sonar rebuild it
This file is at %userprofile%\AppData\Roaming\Cakewalk\SONAR Platinum

Those are quick "off the top of my head" suggestions.

I also have enabled a PCI ASUS sound card which I also set to 44100, 24bit, 256 samples.
I have my realtek onboard card disabled in the BIOS
Some users have seen smoother results after disabling their wireless adapter.
I use enabled wired Ethernet 1gbit/s

The latest drivers are up to date
I dont know what you mean by fully patched windows
I dont know how to check if core parking is off
How do I disable speed step?
Focusrite is plugged directly into usb on back of the computer
I disabled power mamagement on root hubs
I also renamed the aud.ini file and sonar did rebuild it

Fully patched means have you done a Windows update to install the latest patches.

Here is how to disable Core Parking http://www.tomshardware.com/answers/id-2686673/disable-cpu-core-parking.html

Disabling speed step is done in your BIOS.  If you're not sure about this, then best leave that.

One other think I can think of is can you freeze some tracks - especially of the heavier soft synths

I noticed you've mentioned you are using "18" gigs of RAM, perhaps a typo? If not that could very well be your problem, especially if your motherboard supports duel channel memory mode, you need to install matched size and speed memory sticks in pairs. i.e.  2x4=8, 2x8=16, 2x16=32 gigs in order for duel channels to stay in sync and bear equal loads.

I have disabled windows updates to prevent updates for windows 10 and all software synths are up to date
I typed in regedit and then clicked on edit -HKEY_LOCAL_MACHINE\SYSTEM, and then clicked on find, typed in 0cc5b647-c1df-4637-891a-dec35c318583, and checked only the keys box, then set the value max to 0.
Unfortunately I now have a random audio dropout without stuttering.
Steev mentioned the 18gb of ram. There are 3 sticks of 2gb and 3 sticks of 4gb. Could this be a problem?
 

Is there more than one key number to set to zero? 0cc5b647-c1df-4637-891a-dec35c318583. Would they each have a different set of numbers and letters?

I personally would not be using the registry to disable core parking.

I use a utility called ParkControl from https://bitsum.com/parkcontrol/