Just to help your decission....

25mpg

Based on 7000 miles per year (not sure what you do, but short drives = low annual milage), you're using approximatly 280 gallons of fuel, or 1260 litres. This, at 115p/l is about £1450 in fuel alone.

If you fit the ecotek and get a 10% improvement you should be spending about £1345.5 so you save about £100 per year which means you'll have £55 in your pocket by the end of the year or in motoring terms - a tank of fuel

Is it worth it - I'd argue not at today's fuel price but with increasing costs the ecotek looks like it could become a popular mod especially for people doing increased milage

does it void the warenty on the car ?

Tell you what when I have done me Run in miles on me new ST. I will be looking for all the spotty hoodie wearing corsa drivers that pull up next to you in their 1.2 corsa SXI's showing off to their under age school girl totty

I am going to thrash the crap out of them like I used to in me Saxo VTS.
Oh the joy its going to give me.

Oracle9I.

Drove to Manchester from Essex recently and got 39.2 mpg on the journey. Filled up before I left and reset the MPG counter and up until I joined the M6, was getting 42 mpg but once I put foot a little bit, it went down and was on 39.2 when I got to my destination. Average speed was 56 mph according to the computer but that takes into account stopping at lights/junctions and going slower in the roadworks on the M1.