My first 'big' bike was an er5 and I managed to get a full Remus system for it. You wouldn't believe it but that system I had produced the best sound from any bike I've ever had. And several people said that as well. Used to pop and crackle from 40mph downwards - which made the 2 mile commute to University every morning through Glasgow city centre, excellent fun. Literally got EVERYONE's attention. It would do it warm or cold and the system was fitted well so it must have been running incorrectly.
Think I want another now...!!!