Once when I was around 19 working part time at a local bicycle shop as a bike mechanic whilst still studying full time at uni, I had an interesting discussion with this co-worker who was around my age. He had just got his apprenticeship as a mechanic and thought that he was suddenly an engineer, or more precisely - though he was a lot cleverer than he actually was. Repeatedly, he would tell me how the sheer excellence in the Suzuki swift's 1.3 DOHC engine and how it was such a superior engine to that of the Nissan micra.
I used every measurement and fact that I could to attempt to make him understand - "The gti's are tuned very highly from the factory mate, there's not the same initial percentage improvement as there is in a micra with bolt-on exhaust and intake flow modifications. Think about it, the micra has 55kw (quoted - autospeed had dyno'd a standard micra to be well above this), the Gti 74, but the micra also has a restrictive exhaust and TWO, yes two catalytic converters. Imagine the increase by scrapping the whole exhaust and installing extractors and a 2" exhaust." I also brought his attention to the number of successful sportscars Nissan have produced such as the GTR and GTS skylines, the 200sx, the GTiR, ET pulsar, 300zx and many more. I mean you would think that they know how to produce good engines - but it was no use. Facts and numbers seemed all too complicated for this bonehead and I couldn't convince him, all I can say is as a Mechanic I wouldn't let him repair my skateboard let alone my car.
Here's what Autospeed say "Another example where the manufacturer has already wrung the maximum out of the exhaust system is the little Suzuki Swift GTi. In standard form, its high compression 1.3-litre DOHC, 16-valve mill puts out 74.3kW - that's a substantial 57kW per litre (naturally aspirated). With so much effort put in to ensure efficient breathing, you can bet there's not much room for effective bolt-on exhaust mods - and that's been proven time after time on dynamometers around the world."
Now here's where the beauty of a standard micra is - it is exactly the opposite. It is conservatively rated at 55kw with an extremely tiny clogged up exhaust system running two cats. You've probably read on here how well mine went after I put a decent exhaust system right through it - the difference was amazing. After doing the cheap-hack of kinking my fuel pressure regulator as an alternative to me purchasing a uni-chip or similar the car dyno'd at 62.8kw at the wheels.Now autospeed say that the standard micra they tested produced 52kw at the wheels. So mine was around 11kw on top of that before I even constructed and installed my custom intake system. The car had a severe plateau at around 5500rpm which completely dissappeared after installing the custom intake system. The car didn't seem to have any more low down, but certainly above 5000rpm was tremendously better. The only thing I regret is that I didn't go and get it dynod again to see the improvement. However all I can say is that it was noticeably faster than every GTi that I pulled up next to, even one that had a larger than standard exhaust.