I have a picanto 2004 1.1 with 315000 km on the clock. I bought it second hand with 270.000 km almost 3 years ago.
I have done a few modifications and I though to share them with you.
1) because the headlights were faded (the plastic cover gets corroded from UV radiation, especially in Greece with very sunny & hot summers and after so many years) I had them polished and put a special, a bit darker, film on top of them. It look very good and sporty now. The disadvantage is the light is more weak and not so strong. But nothing comes free in this life. This job costed me about 30 EUR while new headlights (after market) will cost much more.
2) New steel white rims. These are very wide so they can accomodate 195/45/14 (offset ET:20 from 35 which is the normal).
The wheels are 1,5 cm out of the car arches. Final outcome may like to some people ...and may not like to others.
But what likes to everyone (even to the KIA GARAGE) is the handling has been masively improved. It feels like another car.
3) KUB shocks with spring buffers.
When I put 4 people and go to highway or other roads..especially the rear suspension seems weak in lumpy roads with high speed.
With spring buffers it feels like I changed springs. I checked the performance and it never touches the bump stops now. I strongly recomend them to people overloading this small car.
4) a small sub woofer at the trunk. It's really tiny from an old fairly cheap samsung home cinema which was to be scrapped. I put the woofer with the use of a good cross over to my cd-radio (very old unit KENWOOD KDC 2031) and I also changed the door speakers with something more decent and slightly larger size at the back doors (alpine speakers) and now..it plays quite decently. I think I can compare the outcome to a stock I30 unit (the comparison is not random, a friend of mine has the car, it's a 2013 model).
5) completely replace the rear silencer with a straight pipe. The silencer is intact...very good quality so I kept it in case I change my mind and want to put it back.
However I found a noticeable difference in performance, especially in high revs (>5000 RPM).
Sound is also..magnificent reminding...much stronger car.
That's all for now.