Okay I have tried and tested by eliminating these possibilities:
1. Cleaned atty and catch cup. Same build, ohms etc. Dripped onto and vaped. No funky taste. So this rules out any residue in the atty or improper build. I have been rebuilding almost 2 years now, so I doubt its that.
2. Squirt juice through the catch cup metal feed pin using a syringe to test the catch cup. No funky taste.
3. Cleaned plastic bottle and silicone tubing. Filled with fresh juice and squonked. First squonk and vape abit, no funky taste. 2nd squonk, I get a hint of that same funky taste/smell. 3rd onwards, thats where is back to having the taste.
Okay my conclusion:
1. Silicone tube gives an off smell when chain vaping and the feed pin at the catch cup gets warm. Not sure if this is remotely possible as I touched the feed pin after chain vaping and it doesnt feel hot hot like on a small atty when it gets during chain vaping. So not really convinced.
2. Plastic bottle and the silicone tube doesnt react well with my ejuice. Although in my experience it hasn't been the case. Smell of the bottle also doesn't give off any funky smell with ejuice inside.
3. Im leaning towards this one. I noticed the silicone tube, when I inhale, some excess juice in the silicone is being sucked towards the catch cup. As I remove the driptip from my mouth, releasing the pressure, the juice flows back down the tube. Now its not like ejuice is being sucked into the atty when I inhale, but more like excess vapor is being sucked back into the silicone tube. Any probable explanation that this hot vapor in the silicone tube will cause reaction and thus give out a plasticky smell the next inhale i take?
Not sure if any of this mean any sense but appreciate the responses so far. I figured this is the best place to ask.