Squeaking at low speed in a 2014 Mazda BT-50

A squeak when taking off from rest could be anything from a brake problem to a wheel bearing fault, a noisy engine drive-belt, bent axle, a dry suspension bush, worn universal joint or just about a hundred other things, including the driveshaft you already suspect.

Of potentially greater concern is the cut-off exhaust system or, more correctly, the previous owner. Anybody who cuts up an exhaust to make more noise is also a likely candidate to have driven the vehicle hard. It might be better to find a vehicle that hasn’t been messed with and potentially abused.

A sawn-off exhaust system shouldn’t harm the turbocharger or engine, but it can make a difference to performance due to reduced back-pressure. It also makes me wonder what else has been changed of fiddled with in the name of more power. Sometimes the performance will actually be improved, but you also open a can of legal and insurance worms by changing things like factory exhaust systems in what is a fairly agricultural way.