I recently acquired an unmolested, all original DT360. Cleaned light rust from tank, installed a Rex’s 12v conversion. It has perfect stainless reed valves in it. Intake has ZERO leaks, as I replaced all gaskets. Carb was cleaned and I went ahead and replaced both jets #180 main and #60 pilot. Clip is set on middle, #3 spot on needle. Idle mixture screw 1.5 turns out and bike idles great and runs florear until mid-range. I tried backing out the idle mixture a full turn, no help. I tried dropping clip down 1 notch to 4th spot. No change….  Anyone have any suggestions???

A quick experiment would be to try it without the airbox lid - some have found this improves matters.

Another possible cause is a bunged up exhaust - chucking it on a fire to burn out the crud is highly recommended by some!

I'm not sure what you mean by "hits midrange"? 

Are you saying it won't rev at all past a certain RPM no matter the throttle position?  Or are you referring to a problem that occurs at half-throttle?

Also is the o-ring that seals the float bowl to the jet setter replaced and in good condition?

It revs and idles perfect. Under load, it starts bogging around 2500 rpm’s. I pulled the plug and it was slightly wet so I have been raising the clip higher and I’m on the highest setting on the needle now and still have some bogging but seems better. 
I did NOT replace the o-ring from the bowl to the jet setter. Only part that didn’t come with my kit. Any idea on what size it is?

And exhaust was cleaned out really good. I actually painted it when I was done. 

O-ring is size 007. I get them at O'Reilly Auto Parts. or the set from Harbor Freight.

Did you use the jets from the kit? These have reportedly caused problems for some folks, so always best to use genuine Mikuni - these are generally still available from Yamaha or Mikuni and are not expensive. Personally, I would use genuine Yamaha 'O' ring, but some folks are happy with the generic ones. 

A good seal on that o-ring is critical. I'd start there. And yes, kit jets and slide needles often cause issues even if stamped the same size. Use genuine Mikuni as Gr8uncleal recommended.

(on the o-ring, the 007 size is correct, the harbor freight metric kit has a bunch or some auto stores carry them as was mentioned.)

You might want to clean your original Jets and replace the ones from the kit back to your originals and needle