If I recall correctly, it is possible to get 100% in Tubelectric. It's kind of hard to help you though, since we can only guess which item you might have missed. You should always watch out for the dastardly "items-that-appear-long-after-you-passed-them" bug.

I have stopped trying to get all items in Jungrock and Sluggion a long time ago. Those levels just look bugged to me. The Jungrock guardian level sort of proves that point (20% enemies upon killing the big lizard, whereas all other episodes give 0% or 100% in their guardian levels)