Hi Vic,
Welcome to the forums! The Echo is a great little car, and amazingly fuel efficient as you have found out. My father owns a gold 2001 Vitz RS (1500cc) and it seems to run on the smell of an oily rag.
Have a search through the Echo/Vitz/Yaris forum to see if there have been any other threads in regards to performance modifications. If you can't find what you're looking for, feel free to start a new thread.
I hope you enjoy it here. Give us a yell if you've got any questions regarding the site