go back to VTNZ and tell them there's no failure. Miraculously, VTNZ couldn't find an issue today either. I guess I must have a self-healing exhaust.
I hear the same issue with VTNZ continuously from various car owners. Not specific to the exhaust but to all aspects to the car testing. I wonder if they would refund you the test for the hassles for the run-a-round?
VTNZ is the last place I would consider taking any vehicle for WOF. Not that they charge a lot more than the others ($10 - $20), their method of testing is a lot different to the rest. (Don't let their TV ads fool you!).
Go ask around car fanatics and classic car people. They'll tell you the problem with VTNZ is the workers there simply don't know enough about all the makes and models of cars and when they don't know, they use an evasive approach which often give incorrect results. They seem to apply a 1 fits all measuring stick rule. This means that they expect old classic cars to have the same tollerance as a 2 or 3 year old Japanese car. They don't understand that not all cars are built to the same exact tollerance.
A good example is the old Minis. Most workers at VTNZ don't realise that the steering ball joint has a spring inside. With their evasive approach, and the small wheel on the mini, it's not hard to excessively show the wear on the ball joint when they're just really depressing the spring. I speak from experience.
The overall approach is flawed. It should not be "we must try to fail WoF on every customer". Such as lifting the steering wheel up and down on a car to the point that it excessively flexes the steering. They really check out for excessive wear by prying with metal crow bars under the vehicle. The experience is stressful because they're doing tests that are beyond the normal use of how the car drives on the road. This is why cars more often fail at VTNZ than most other WoF garages. If there's 2mm if play in the ball joint, it fails. Whereas over in N. America you have 330 million people, with all the cars on the road we don't hear of cases where a person loses control of a car because the steering rod falls out of the ball joint. The issue is that the driver would know that a car becames so difficult to steer (because of the excessive ball joint play) that this annoyance would force them to repair it at the garage. Meaning, the driveablity of a vehicle isn't determined whether the ball joint will fall out but rather, determined if the car can properly steer. There is A LOT OF WASTE of throwing auto parts away in NZ because they're not fully worn to acceptable levels. Hence VTNZ's 1 measuring stick rule.
Unlike their TV ad claims, the workers at VTNZ do not treat their job as their lifelong career. Not even comparable to the local garage mechanic who's been working on cars for decades. The local garage mechanic runs it as their own business. The VTNZ employee is just only concerned about their paycheque every 2 weeks. So how or why would it be possible for such workers at VTNZ to know as much info about makes and models as the local car dealership or the petro station garages?