Hate to burst your bubble guys but while there are numerous genuine benefits to a bigger exhaust system, going overkill on size could be one of the biggest and most costly mistakes you'll make.
Sure, bigger pipe size and straight through muffler internals = better flow, BUT, in the highly technical world of performance exhaust enhancements, one thing remains the same....the need for backpressure. Without this, you ain't goin' anywhere.
While it may not be possible to achieve that 'V8 burble' on your mum's Barina, it is possible to make it that little pocket rocket that you've always dreamed about. With society's demand for vehicle manufacturers to make smaller, cheaper and more efficient cars, performance enhancements are a big market. Get it right and you'll be the talk of the town, get it wrong, and you are tearing up money.....or your next default notice.
When it comes to optimum exhaust performance, best leave it to the experts and get some good quality advice.