Growling noise when accelerating

[Douvan]

Hey everyone

Had to get the whole exhaust changed at the weekend at the garage after the original piece had rusted somewhat and had a few leaks.

First day of driving with the new exhaust and when driving at speed, roughly 70mph on motorways, a sort of growling noise has developed when pressing the accelerator. As soon as I lift off, the noise goes. There's also no noise when on normal streets, just when getting up to motorway speeds. Any advice would be appreciated.

It's an 02 Yaris VVT-i

Thanks