Leak would cause a high idle.. but it wouldnt cause the revs to go up and down like that... IMO... If it is a leak tho there is a dead easy way to find it... Take the boost pipe off and put your hand over the throttle body... It will suck. If it cuts out. Its not a leak.... If it doesn't cut out the revs will get lower, you should hear a sucking noise from where the leak is...