Ok, so I loved the motogpwerks stainless pipe because; 1. Its stainless 2. the smooth bends looked great. The problem was the fit on my F bike (taller oil cooler/filter) would hit the pipe because of lack of clearance. So if I ran this pipe I would have to remove the pipes each time I wanted to change the oil. This would not be a problem on a K bike because K's do not have the additional puck under the filter housing added to F bikes for extra cooling.
So I picked up the next best option, IMO, for a 4-1 besides running a Kerker. The fitment issue was driving me crazy so I broke down and got a Yamiya (model - 70mm-L size). Not 100% sure about the difference in the pipes yamiya sells but I believe the 70mm L pipe has a larger circumference muffler tube and looks to be longer than the yamiya pipes sold on ebay. I ordered the pipe directly from yamiya from the website and got a little price break versus ebay. The pipe was at my door in less than one week (I was shocked because of the unfortunate disaster). Finish on the pipe is great and I could not be happier, unless it was stainless. I am not too stoked on the welded bends, but I would rather have a pipe that fits better than have smooth bends, and I am sure performance difference is negligible. Also I love the look of the swan neck bends from the head to the collector.
Here are some pics for comparison.
Yamiya
MotoGP