Thierry,
If your engine is running on all six cylinders now, make sure your linkages are still correct, make sure your WRD is closing, make sure your cold start valve is not leaking, make sure your timing is correct and make sure all is in good tune. Your fuel pressure should be up to specs. Now if it is still running rich, you can remove some round shims under the Barometric compenstator (altitude sensor). Removing one or more round shims will cause the engine to run leaner at ALL speed ranges.