do they work?

had one on my polo coudn't see much diff but i raised the topic few weeks back and i got the same answer but with evidence that they do more harm than good, but on a normally aspirated engine i can't say it would got a blue one if your interested £20
 
not on a stock car no. BUT...I have one on mk2 with a rally spec 2 litre motor with shcrick cam and it has a little bit of a lumpy tickover that would not pass its MOT.......until I had the ecoteck fitted by Vince at Stelath.........and mysteriously, the tickover improved and it flew through its MOT too! Not just passing, but passing easily!
They work by bleeding a small amount of air into the inlet increasing swirl and on the highly cammed motor I havem at low rpm its very inefficient and the mixture is pretty rich with high hydrocarbons.

But the ecotek did work and work well.