I recently installed a new Dr D head pipe on my 2011. I started with the slip on so I had to order direct from Dr D (for some reason nobody sold just the header). They addressed the oil filter clearance issue (which frankly did not bother me). I would have been fine with the bigger bend. It is a few mm larger than stock but seems to flow a good bit better. It was fairly easy other than removing the alum collar they use to neck down the slip on for the stock header. I can offer a few pointers on that trick if anyone is cool without using that collar again. My seat of the pants dyno notices it. It has a less abrupt pull off the bottom with more in the mid range. I mostly did it in anticipation of future mods. It was still a worthwhile move.