I've had great results using FactoryPro jets. My understanding is "Genuine" means jets from the manufacturer of the carburetor and will have the company name stamped on them. OEM is just that.
http://factorypro.com/Keihin (it's "kayheen" with accent on second syllable )
Unlike other jet companies (dj, rd, keyster), Factory Pro Replica jets, Keihin and Mikuni, follow the original manufacturer's size scale so the Factory Pro Replica jets are interchangeable with original jets - saving a lot of time and improving accuracy for a good tuner.