BMW R850 Maintenance Manual page 90

I was very pleased with the improvement in throttle response, low and mid range
power, and about a 5-10% increase in fuel economy! I noted smaller throttle
openings for a given cruising speed and a complete lack of backfiring that my RS
had always suffered from with the Staintune "touring" system I have installed.
With smaller throttle openings for a given load, accurate throttle body synch
adjustment will be more important. Nonetheless, I was delighted with the results!
In summary, I think the GS intake manifolds with GS Cat Code Plug is an
effective and inexpensive modification that will give an RS/RT more "grunt"
where most riders need it, with little top end sacrifice. Heck, do most of us really
need increased performance above 6500 RPM (120 MPH+)? That's where the
above reported horsepower figures intersect. I'll settle for "real world" roll-on
improvements with inexpensive BMW parts!
Note: The GS Cat Code Plug can, in some instances, cause hard starting and
cold running problems in some RT's and RS's. If this is the case on your bike,
simply revert to the standard Yellow Cat Code Plug. Most of the performance
benefits from this modification are derived from the intake manifolds.
90