Need some needle advice

Okay... So I am getting really close to getting my single VM34 tuned for my KZ400. But I THINK I need a different needle.

Wondering if you guys can help me figure out which needle I need...

I am pretty sure I have my main jet dialed in at a 145. If I go down to a 140, I have very little power at full throttle. But 145 seams good.

The reason I think I need a different needle is because even with the 145 main, and needle at it's leanest setting, I still get popping when I ease off of the throttle.

Does this mean I need a leaner needle, or a richer needle? My current needle is a 6DH4. According to this chart there are quite a few 6 series needles: www.jetsrus.com/a_jets_by_carburetor_type/needle_mikuni.html

Should I go to a 6DH2 or a 6DH7? Or to a completely different needle?

Thanks in advance for any input.

I should also point out that while I am getting "popping" when easing off the throttle, my plugs are still super black. But I can't figure out where the hell I'm rich because it doesn't "act" rich anywhere!!

After reading this document: www.mikuni.com/pdf/vmmanual.pdf I think my issue may actually be my pilot jet being too lean, not my needle! Apparently the needle doesn't come into play until about 3/4 throttle. I am popping when rolling off of the throttle at 1/4-1/2 throttle. Guess I'll go UP on my pilot and see what happens!

This would make sense also because with my 25 pilot, my air screw is almost all the way in. If I go up a size or two I should be able to lean it out accordingly with the air screw.