The way I look at the exhaust is from the back to the front. ABE will give you X increase in HP, CBE will give you X+Y, and a TBE will give you X+Y+Z. It's a weird way to look at it, so I hope you can follow my train of thought. If you have a downpipe already, adding a CBE will give you a "modified" TBE IMO. Noticeable gains, but I'm not sure if it can be called a TRUE TBE.Are there any power benefits to getting a pure CBE (like the soon to be released SPT package) if you have a downpipe and EM? Better phrased, are the HP gains culmulative?