If you are going to gut your pre-cats why do you need a "high-flow cat"? If your other cats aren't clogged don't replace them. A "high-flow cat" is designed to replace the 70's bead type cats, which are very restrictive. The style on your car are the monolith type that flow a suprisingly (sp?) large amount of air. The high-flows are the monolith style too.
