Perhaps I'm missing something here, but I'm not quite sure why you are trying to "box" your tasks in. Part of the listed job responsibilities of many higher-tiered workers is precisely to help and educate the ones in the lower tier so they can rise up and do better. It sounds like your manager is delegating more responsibility to you because s/he trusts your judgment, and part of your success may be to form some kind of training or knowledge base that they can consult on their own, which would relieve YOUR burden. That is a positive thing, and you should make a note of it and any other out-of-the-ordinary tasks for mention of your value during your next review. When you can bring up solid evidence of making things better or helping relieve the manager of their burden, they will be more inclined to promote you or give you a raise.
If, on the other hand, you feel that these additional requests are causing your Level 2 work to actually suffer, you will need to let the manager know that you "are more inclined to perform to the best of your ability" or "in a better position to expand your capabilities" if you were free to focus more on your work level, and give solid evidence why.
No one is exempt from doing SOME work they don't like, and I personally respect people who have no boundaries in doing any kind of work. Some of my best bosses were people who were down with us grunts sharing our work to help out when needed, and I've always looked up to the people in the know who bothered to help me even when it was surely trivial to them, which is why I make an effort to do the same. I also know when I have taken an interest in helping those in more junior positions, even when my colleagues make fun of me for it, that high-ranking people have seen it, taken note, and approved of me publically.
It is apparent that the department needs help and the manager looks to you for support of the crew or SLAs. You can choose to bear it with a smile, present documentation of the fulfilled requests and a hope for a higher paycheck, or you can go to them and let them know you aren't comfortable with the way things are, possibly putting you on a path away from success. IMHO, the good guys win in the end and I would choose the former.