Hummer H2 Borla Exhaust System. ORLA exhausts are built of aircraft-quality T-304 stainless steel -- stainless inside and out. Borla's free-flow exhaust utilizes patented award and race winning technology to deliver quality, sound, performance gains and enhanced fuel economy — all with an easy bolt-on installation. All BORLA street products carry an unsurpassed written million-mile warranty. Gains are usually 7-10% increase in HP.