my mates corsa 2ltr 16v c20xe has'nt been runnin properly , so we've stripped the engine down , found that the headgasket has kindof gone . but whilst we was taking the head off we noticed that on the passenger side of the fuel rail theres a black/silver box type thing , it has what looks like a breather pipe going to the bottom of the throttle bodie . problem is ive looked on a friends cav gsi and he has the same thing the box with a pipe goin to the throttle bodie , BUT , he also has another pipe coming out of this box which goes over the engine and looks to be going into the bulkhead . problem is my mate has'nt got this other pipe on his corsa , it is missing . So i was just wondering what it is and would that make the car run crap ?? cheers for any help .