I can imagine blocked DPFs killing a lot of black cab and bus engines.
Busses are generally serviced very frequently so that would overcome that issue for them, as for Taxi's I know that until very recently (may still be the case) a lot of black cabs don't have DPF's fitted.
Busses are generally serviced very frequently so that would overcome that issue for them, as for Taxi's I know that until very recently (may still be the case) a lot of black cabs don't have DPF's fitted.