Congratulations!
The Sigma engine is very satisfying in the high revving ( from 3000 to 6000 RPM )
A cheap and effective conversion may be changing to an open air filter system from K & N (kit number 57-0686 for the Ford Focus II engine);
It consists in getting rid of the closed air filter box (very difficult to change the air filter element) and install the open air K & N air filter just in front of the induction pipe (short elbow type of tubing).
IMHO it produces a better sound, more tractability and better under bonnet looks.
If you want I can send you some pictures of my conversion (4/4 Sport 2009).
Just give your e-mail address
Kind regards,
Bart D'herde
