As I'v stated for over the past year the DVP needle with YZ timing is an excellent all around performer and tough to beat. In So Cal between 1000 and 6000 feet I run the DVP #4, a 48PJ, fuel screw between 1.0 to 2.0 turns and a 180 or 178 MJ.
At altitudes above 6000 if I will be at that altitude for a while (couple of days, etc) I will run a DVR needle in the #4 or #5 and a 175 MJ.
As to the recent jetting experimentation using the E** needles its been a tough search and I'v setteled on a EMN needle with a slight mod to make it look like a DVP #4 between 0 to approx 1/2 throttle and then the standard EMN above that. This needle also works excellent but I still occasionlay get some odd stumble but not often. If I'm riding hard with lots of throttle operation its fine. Its when crusing that I notice the occasional and I mean very occasional stumble. I'm running EMN mod #3, 48PJ 1.5 fuel screw, 165MJ.
I'll run this for a little longer and then go back to the DVP and based on this make a final decision on what to run long term.
I concur with James Deans observations about the exhaust
if you have a good flowing exhaust it will be more compatible with the "E" taper. And lastly my bike is a 420 running a 13.5 to 1 Weisco piston, its been ported and I'v run the Stroker and FMF
PCIV-2 spark arrested exhausts. If I still had my WB which I sold to Bryan I bet it would be more compatible with the "E" taper yet.
One thing I noticed since I installed the 420 kit I cannot hit the rev limiter with the Vortex
ignition. With the standard 400 configuration I hit it regularly. I feel Its fighting the 13.5 to 1 compression as the revs build and cannot get there. The bike rips on the bottom and mid range but on top the 400 was faster. If I went back to a loud performance exhaust probably would get a few more R's but my head would be hurting. The bike is a much better trail and dual sport mount now than before by quite a large margin--more torque, predictable slow speed operation, less stalling and pulls taller gearing easily for street crusing.