Yeah, I cleaned this one before I ever installed it. NO way was it over-oiled. The stupid thing went into limp mode just idling before I ever drove it. Everything was sealed up tight, and the MAF looked clean when I pulled it. It must not have liked the flow rate because when I installed a new GM filter, it went right back to normal. I'm generally not a fan of over-paying for factory stuff, but in this case it seems to be worth it. Once my truck is out of warranty, I'll start messing with it a little more.
You guys that are running K&N, is it on an LMM? I had a K&N on my 04 without a problem, but A LOT of people seem to dislike them on this engine...