No problems at all. My bike rides better than stock now.
If you've fitted Remus headers to a late model 1200 then, at the very least, I'd suggest getting it on the dyno to have the AFR's checked with a view to altering the fuelling if necessary. I know that when the first 1200's were introduced, both Remus and Akrapovič marketed their headers with the claim that were was no need to alter the fuelling. However, that was 10 years ago now and the fuel maps have become progressively leaner over the years.
I fitted Remus headers to my '04 R1200 GS and it ran well with all the fuel maps that were updated at each service. However, fitting the same headers to my '07 bike produced noticably higher exhaust gas temperatures. This discouraged me from fitting the same headers to my '09 bike and then the '11 had a different system with the "exup" valve, although it would have been possible to remove that.
It's a common myth that the injection system will compensate for any and all intake and exhaust modifications. It'll only achieve that when the engine is running in closed-loop mode, ie at relatively low revs and small throttle opening and then only if the fuelling requirements are within the parameters of the ECU map + trims. It won't adjust itself when running in open-loop mode, ie large throttle openings and high revs and that's where an overly lean mixture presents the greatest risk to engine life.
To achieve a complete level of adaptability would require wideband lambda sensors and an adaptive ECU, e.g. a Power Commander V with Autotune module.
"A map is not the territory it represents, but if correct, it has a similar structure to the territory, which accounts for its usefulness". Alfred Korzybski
My header was replaced by David Benda, owner of Bavarian Cycle Works in SF. He has been wrenching on these bikes for more than 30 years and is a factory trained technition. He did the same thing to his 2009 GSA and like mine he has had no issues what so ever. This man has forgotten more about BMWs than most of us will ever know, I trust his judgement.
I cut the oem cat out of my stock headers easy job just cut 1/8"in front of rear weld at cat canister use flat bladed screw drivers and wiggle the insert until small weld at front of canister breaks away and out it comes then a trip to the exhaust shop to weld the heaust back together already have a remus muffler
end result much more power the fuel usage went from 5.4lt/100k to 4.5lt/100k as expected with the flow improved the engine is running lean and now needs to have the ecu remapped. It seems in England they are remapping the oem ecu but here in Australia it is a case of fitting a Power Commander or equivilent after market controller to up the fueling in line with the extra flow of air