i had the same k340 like yours, green driver, grey passive radiator. Just tried the half-cotton mod. Man,what a difference. I though my pair was bass-light but now I no long think it is bass light. with half cotton removed, it sounds open, flat and coherent.
Now I start to understand what an amazing pair of headphone K340 is. Glad I got one almost new pair from ebay. Paid a lot but its worth it.