Both UNI and K&N will be noticeably better than stock. I doubt anyone can tell the difference between the two. I like the UNI as it is very easy to clean and re-oil. I only lightly oil but feel the oil helps in retaining small dust particles.
I'd try it with the new filter, bellmouth, and snorkel removed before cutting the bottom out. You may find that unnecessary. You may also need to change your main jet with the increased airflow.
The two snorkels on the inside were only on 04 or earlier models. Yes, remove them as well. They were taken off of all factory models by 2005.
