a couple of years ago ecotek had to change their marketing after they couldn't prove their claims. the conclusion of an independant tribunal was that the ecoteck valve does not improve performance (power or torque) and does not affect fuel consumption (mpg). the only claim thay are legally allowed to make is that the ecotek valve improves the driveability of the car. thats a fairly broad thing to say and doesnt mean much.
the actual effect is the revs drop slower when you lift off the accelerator pedal because a small amount of air is bled into the inlet manifold during lift off. the "swirl" effect makes no difference, that has been proven. the air bleed on lift off produces acceleration gains by making revs higher at gearchange during hard acceleraiton, however the negative effect is reduced vacuum assistance to the brake servo during decelleration, the one time you need the assitance. it doesnt make the brakes less effective, but you will need to press the pedal slightly harder than without the ecotek valve fitted. most people dont notice this affect proving it isnt worth worrying about.
overall they arent a bad thing to hav on your car, it wont damage anything, but dont expect any real gains in performance or fuel economy. if it really worked every car would have one as standard. besides the noise is a bit crap, especially when they are new.
