Wonder if its worth doing a sniff test just to make sure.
Sooner rather than later, think I would drop the garage a letter or email, so you have a paper trail soon as you have recognised the problem.
Dont know what cover you have, but the garage must meet their obligations in selling you a car "fit for use".
Get it flagged up with them as they are the one that must sort it in the first place.
Hope its nothing.
Might pay you to pm Flying Banana he has a 1.8T plus a big monster. He might have more idea on ZT's.
