04 to -6 systems
scotts,
All the MBRP and AFE systems we sell will work on any 2001-07 truck! BUTTTTT you will not be able to reinstall the cat on 2006+ trucks if you use a 2001-04 system as they used a 4 bolt flange system to attach the cat to the balance of the system while the 2006+ trucks use a butt joint with a band clamp. Operationally the systems will bolt in if it's a front pipe and cat back system or a true off road system, but if you need to reinstall the cat to keep the local emmissions or dealer happy you'll need to bolt the stock system back on. If you have any questions let us know we have been selling the systems since day one!!
Mark @ DPPI