slurrrp slurrrp rasp!!!
thats what they sound like. I bought an ecotek device ages ago, but never got round to fitting it, well once fitted it does take a while to get used to the strange noises it makes, especially when first running it in
My general opinion is that they do in fact work, my mk1 172 is chipped and was managing approx 28/29 mpg, after fitting the ecotek the mpg is about 31 and about 36/37 on the motorway.
I cant say that ive had any performance increase, but i wasn;t expecting any... hope this onfo helps
cheers
Jase