Hi Guys,
Yes the Coby extractors are "dodgy", but they are good value for money.
They're cheap - not a lot of engineering could have gone into them.
However, we know they smooth the power and torque curves of the engine, improving drivability. The engine feels a LOT more torquey at lower revs and pulls well from about 2500rpm.
For me it was so noticable that on roads I drive regularly I could use 5th where before I had to use 4th.
So while they are definitely not optimal from a performance point of view (as dondesoto showed us), I reckon they do a great job for the money.
Cheers,
Greg