Skunk2 Racing SKUNK 413 05 6070 Mega Power Double Barrel Exhaust 3 Skunk2 Exhaust Honda Civic Si Sedan Coupe (17 21) 3" Catback w Double Skunk2 Mega Power Double Barrel Exhaust 17 20 Civic Si JHPUSA Skunk2 MegaPower RR Exhaust (76mm) 06 11 Civic Si Coupe JHPUSA. The 76mm MegaPower Double Barrel (DB) exhaust system features 304 Stainless Steel, CNC Mandrel bent piping and robotically TIG welded joints for the highest strength and exhaust flow. Coupled with a minimally restrictive resonator and parallel, twin straight through race mufflers, this exhaust matches maximum performance with maximum style.