2005 Primastar Noisy Air Intake Above 50mph?

Above 50mph there's a deep sound like a Boy Racer's car exhaust. I thought it was the exhaust at first but Kwik-Fit say there's nothing wrong there and think it's the intake manifold.

I'd just like to hear if anyone's got any ideas. One thing I've noticed is that one of the temperature plunge sensors is corroded and disconnected.

You can hear the sound a bit at around 30-50mph, but hitting 50 and it really kicks in

Thanks in advance