Gearheaddave is right about the fact that the post count doesn't mean you arn't experienced & that someone is just new to this form.. but anyways. I experienced a backpressure issue last year with my nitrous setup & bad timing .. i didn't have ANY back pressure & it caused problems with my valves. With my experience bing in a custom pipe bending shop with my uncle. On small engines that are turbo charged such as mine, the turbo is all the back pressure needed & actually almost to much. Cat's do increase backpressure but in the case of a stock motor, even with some bolt-on's i would leave the cat there becaues you will some low end power (yes enough to be noticable). Hope this can help somone out there!