I took a quick look at this. I plotted the % discount to the price of KMP stock. The graph looks like a column with a very slight left to right downward tilt, i.e. the spread narrows as KMP goes up. The previous time I looked, the line had a much more pronounced negative slope, i.e. that the discount narrows consistently as the price of KMP goes up.
I'd say old relationship no longer holds. This would mean, I think, that KMP/KMR are set to trade at basically a higher level, probably due to the EP takeover. I still think it is too early for this much of a ramp, but that is what the data says.
I have been lazy recently (or busy at work...same outcome), and haven't updated my KMP/KMR analysis since July. I will update it towards the end of this month for a year end(ish) update. For now let me reference those posts.
The basic conclusion is it you want to buy KMR when its price is relatively low compared with KMP, and buy KMP when it is relatively low. This is simple "buy low, sell high" thinking.
When KMR's discount is big, think of it as being 'on sale'. In the past few years about 11 or 12% has been typical, so KMR has been on sale when the discount is pushing 15%. When the discount is low (about 10%) KMR is NOT on sale...that is pushing the full price limit.
Keep in mind that the previous paragraph is based on data through July '11. But the pattern has been pretty steady since the recovery from the 07/08 market meltdown. I would be surprised if the past 5 months have changed it that much. Then again, that's why you do analysis; if you know all the answers why bother looking at the data and doing analysis? You know you are right, and all you might find is the data is wrong ;) There is a lot of that type of thinking going on around Capital Hill and on the campaign trail these days.