The R-9 and GS-1000 are really mid-weight "magnum" airguns anyway. That is, they shoot in the 12 to 16ftlb area. The pellet weight that is GENERALLY the optimum is between 7.5gr and 9.0gr for .177 cal. This is to insure long spring life and optimal performance.
All air rifles of this type "diesel" to some extent. The problems start when COMBUSTION takes place. Also, the newer the gun, the more it tends to smoke a little. Pull a patch down the bore to remove any xs lubes and avoid lubes on your pellets to minimize the smoking.
The Barracudas(Beeman Kodiaks) are great shooting pellets. They are GENERALLY thought to be a little heavy for an R-9. But really, shooting them probably won't hurt a thing...