go to an exhaust shop and have them make a "test" pipe. Goes in place of the cat as a way to test if the cat is clogged...this is what my local muffler shop will do. But for some reason they wouldnt do new head pipes from the headers into the cat for me. But in all honesty I'd rather have a cat, better throttle response decent tone. I had the stock one gutted, and it acts as an expantion chamber and kinda makes it sound raspy and annoying in the cab