Choose Options Cummins ISX15 X15 Big Boss Stage 1 Performance Kit By PDI Performance Diesel MSRP: Now: $3,989.95 Was: Cummins ISX15 X15 Big Boss Stage 1 Performance Kit By PDI *This product is NOT legal in California. Raney's is not responsible for legal ramifications. Big Boss Stage 1 Performance Kit Fits Cummins ISX15 And X15 Engines Available For Years 2011-2013... MSRP: Now: $3,989.95 Was: Choose Options