2 Here’s the 49-state legal BBK Performance #1509 CNC Series Short High-Flow catalytic converter package with 2-1/2-inch plumbing for Fox-body Mustangs. The BBK cat package is not smog legal in California, where the stock four-cat package is mandatory. We’re not sure when the exhaust hangers changed from parallel hangers (#1509) to perpendicular hangers. However, if you have perpendicular hangers, you will want the BBK Performance #1563 cat package. California enthusiasts will have to have an exhaust shop fabricate a four-cat package from scratch using smog-legal cats because we haven’t been able to local a complete four-cat H-pipe package from the aftermarket. If you can find a new-old-stock four-cat H-pipe package for your Fox-body Mustang, buy it. You can get into the BBK cat system for under $400.