Big Oil is simply adding another pump to the factory pump. The Stealth and Terminator systems add another factory pump via and adaptor to the existing one. The BTS pump adds a 530 pump and stacks it on the factory hpop.
www.beansdieselperformance.com home of the Stealth
www.diperformance.com home of the Terminator
www.brianstruckshop.com home of the bts stacked pump