Originally Posted by diesel

i had exacly the same problem with the revs going up and down it does it in perfect timing to, up down up down etc... i tryed every thing, breathers, boost pipes, sensors, the lot, i change the meter unit in the end and problem solved it had me for months a propper headach

hope this helps if you come to nothing with anything else it was my last choice and it worked

Originally Posted by Rob_DOHC

I think thats pretty conclusive mate. If you want to solve the problem, replace the dump valve (if thats what is leaking). You could always try removing it and seeing if the problem goes.