Short journeys clog them up badly and seize the vanes in the exhaust housing. But it's an easy fix if that's the case. Take the exhaust housing off and check the vanes, if clogged up with soot spray cilit bang foam spray on the vanes, leave it for a few minutes and clean up making sure the vanes move freely back and forth. Loads of turbos have been replaced when all they needed was a good clean. There's a few videos on YouTube on how to do it. When I bought my ST tdci it was sluggish and a bit smokey on full throttle but after a dam good thrashing it sorted itself out. I do a lot of miles in mine and it's been fine, but like I say they hate being pottered about in.