Hi.
I have got blowby problems on my XK8.

I cleaned the breathers , paying particular attention to the small breather 2.5mm hole. This made no difference.
However, Ive just repaired the heater pump, way down under the expansion tank. In the process, I snapped the brittle plastic flexi tube, about 10mm diameter. This was connected to a T piece into the throttle body, and then, I am sure, without taking too much off the car, it went to the small breather on top of the lhs cam cover.
The other end went under the expansion tank to a rigid metal pipe that seems to exit out into the front wheelarch. I will have to remove the inner wheelarch plastic cover to confirm this.
Now, the point is, that this metal pipe is blocked completely, cant blow or suck through it. When I ran the car, I disconnected the breather pipe from this metal pipe, and there was a lot of hissing, suction from the breather. After a minute or 2, the car started to run rough, so I put the pipe back on to the blocked pipe, and it ran better.
Can anyone tell me if this metal pipe that is blocked should be open, closed or partially open? I cant see the point of having it if it is closed, but if it is fully open, it seems that the car runs rough.
Ide like to investigate forarmed with as much info as possible, so any advice will be gratefully recieved.

Cheers.

Paul