Bought the wife a focus Since then I've had to replace a few bits and pieces, including the cat and more recently the idle speed control valve.

However, it was replaced with a mondeo one (looking on ebay, it looks like they're the same fitment)

I have air resonating in the air filter, I've taken off the pipe work to just leave the throttle body exposed, started the car and it's still doing it. I can hear air coming from the throttle body.

The only thing i can think of is the idle control valve is the wrong one, but does anyone have any ideas?

2.0 Zetec 2001 by the way.