dont know about the XR but the RR standard headers are very difficult to improve on power wise, they are a work of art the main reason for buying after market exhausts is mainly for cosmetic reasons as the manufacurers have upped their game..i was at hilltop when 2 guys had the new R1s remapped 1 had a full Ti Akra and the other a full standard system, after several runs trying the standard system produced more power
I have heard that. The main reason I got the headers is for the sound, and the clean look without the cat. I may go down the PC5 route this time, and compare back to back with the hilltop map on the GSA to see which is better.
If you have an XR and want a locking sat nav, you can buy all the parts from BMW for around £40, then don't have to worry about some toe rag nicking your nav when you park up somewhere.
The only slight issue (and why BMW didn't fit one in the factory), is that you have to rotate the whole unit up, whenever you want to remove the nav. This isn't a major issue, and is made easier if you have the emergency wallet key, as you won't have to rotate the unit as much.
If you want a list of part numbers, let me know, but here are some pictures of the parts, and the fitted product.