Just my opinion but I say if you want to change the silencer to change the sound, or to save weight, or to change the looks, go for it.If your wanting to see any real gain in horsepower you'll probably be disappointed.I've seen some that thought they got a bit of power increase at max rpm speeds but they also lost some of the mid and low speed torque.As for the Power Commander, the folks who have bought them seem to have seen smoother running engines, less dying at stop lights and a real or imagined increase in power.I suspect most of it was imagined.The Royal Enfield UCE's as they come from the factory are pretty much maxed out on their power delivery. To gain any real horsepower, you'll have to get the cylinder head modified along with the cam's.Ace is working on the best way to accomplish this but he's still in the development phase of the program.
I changed my exhaust and air filter, the stock ECU is working good for me.
Here is a little tip: When removing the stock muffler be sure to remove the heat shield first before you do anything else. The exhaust pipe has a hook welded to the end of the pipe (see photos) that the heat shield connects to and secures the entire muffler to the engine header pipe. If you don't remove the heat shield, the stock muffler will not come off. No such problem with the accessory silencer, though.