A late evening Denver, CO to Laurel, MT (DENLAU) manifest appeared on the BNSF Front Range Sub sporting foreign power. Not just one but three NS GEVOs. Leading was NS 7543 followed by NS 7521 and NS 7671. This 109 car train, stopped for about 30 minutes on the main at Longs Peak Siding. The reason for stopping was due to the detector indicating that they had an extra car, so the Conductor had to investigate. Then they departed for Cheyenne.