To save folk looking, I have taken this from the ADVRider site:-
FUELING ISSUES
There has been a great deal of talk about fuelling issues on the R1150GS and R1200GS when fitting Remus or Akrapovic exhausts.
Here are the facts from the tech guru at the importers of both makes of exhausts:
'' We looked specifically at the 1200GS and if you recall I spoke at length with Remus and the long term testers such as Peter Baker from MCN who ran a Remus complete system on his 1200GS for the whole of the 2004 season without any issues whatsoever, and after contacting several key dealers none of them are reporting any fuelling issues whatsoever with a standard air filter.
If you recall Ride Magazine also ran a Remus for several months earlier this year prior to fitting the Akrapovic and reported no problems at all.
It's fair to say that an after-market fuelling chip or TFI kit will refine and optimise the fuelling but this applies to any make and model of bike and any make of exhaust - not just a BMW with a Remus or Akrapovic - it will make the power delivery smoother and improve throttle response - as we know it refines the air and fuel ratios but I want to stress this is not necessary - it's optional. All fuel injected bikes can benefit from optimization of the fuelling (even from new - when the bikes have been supplied to meet very stringent emmision requirement) and Remus have identified this and are developing a fuel control module that will fit many bikes - Japanese, Italian and German.
"To clarify; Remus and Akrapovic carry out extensive research on their products and sell them on the understanding that no fuelling changes are necessary, but can be considered as an optional improvement by the owner if required.
"I have also pasted a link to the official Akrapovic site that clearly states their policy on this matter and the policy is an exactly mirror of the Remus policy on this subject. the link is below but the section reads as follows;
'The Bolt-On, Slip-On, Sport Production, Racing, Evolution and Street Legal ranges are designed to function properly using the stock carburettor or electronic fuel injection set-ups. This means that no changes to the stock set-ups are necessary in order to use Akrapovic exhaust systems. Also, all of the performance specifications which we measure and list for each exhaust system model are based on stock set-ups. We assume full responsibility for the accuracy of these specifications. However, we also believe that it is possible to improve the original set-ups when our exhaust systems are used.'
http://www.akrapovic-exhaust.com/main/faq/faq.htm
"In addition any issues concerning 'popping' or backfiring on the overrun are due to air leaks in the system. On overrun a vacuum forms in the system and air will be drawn in through any gaps and may even cause flames to appear out of the back of the exhaust. If it is a new system, generally it will seal after the first few runs otherwise normal clear silicon bath sealer (really! - as used by all the race teams) can be used to seal any air leaks."
Not withstanding the £600 fine and the 6 points in one hit. 
