The length of the ER intercooler lower pipe should be the same length as the stock lower intercooler pipe. (same goes for ETS intercoolers too).
Therefore the replacement of the Upper Er Pipe should be the same size as the vishnu charge pipe. The only difference may be if you have a 2007-2008 ER pipe, that utilizes the stock rubber elbow. Then you may need to remove your stock rubber elbow. Otherwise the long version ER CP (2009+) would not utilize the stock rubber elbow.
The stock rubber elbow is between the upper and lower post intercooler piping piping.
Historically its been a super tight fit. You just need to get your hands dirty.
Unless something is different about your setup drastically (and i dont see why), everything should fit.