I have a similar machine, and have successfully used it with a whip. But I am concerned if you are tasting plastic, that is usually associated with burning it for me. Also with weed in there you have competing vapors.
My best results are setting the temp to 170C (this is far too low for your herbs), and using a metal oil pad rather than leaf (as leaf is not very conductive) - I bought a few different pads until I got some that fit.
Then after it reaches temperature give it 30 secs or so until you can see the vapor seeping out of the mouthpiece - then its ready.
It takes a while to start producing it thick enough for a breakthrough even then. Usually its the second pull that is the thick one and will get you there. I usually load between 30mg and 40mg and I am sure it is not very efficient, but you need that much to ensure you can get enough in one go. This is where a bag makes the difference, because although the early stuff is weak, the really thick stuff evens it out. Still always a 2 pull job from a bag too.
For making my breakthroughs consistently certain:
1. Full deep breath and hold them for 20.
2. Lay back and really relax, as if going to sleep (with a bag/whip you can do this before even the first pull - I once had a breakthrough where I held on to the tube, and I felt another part of me take a 3rd pull whilst I was in hyperspace - it did not prolong it, but did shift the tempo!)
3. close eyes, and/or use a blindfold.
4. Exhale that last one and let go.
GVG or equivalent sounds to be more effective and more efficient - but I love the lack of messing about before launch, no flames, no hot device, no bright flame light, no worries.
I speak as if it were fact, but indeed this is just the insane ramblings of my ego - but my inner self seems to be nodding.