Your money is much better spent on an intake upgrade.
There is a notiecable increase in power, and it make the engine sound more angrey....
Don't you want an angrey sounding 1.6 engine with 4 pistons of terror going down the road?
But seriously, be careful with alot of the "upgrades" on ebay, if they were so great wouldn't one of the mfrs be selling them and making money on them to.
If it sounds too good to be true, then it probably is.