The Mitsubishi Pajero is actually regarded as a very reliable vehicle, so your experience is not typical. There are several potential causes for this, but the thing I’d check first would be the air filter. Is it possible this was overlooked during the recent service? A blocked or dirty air filter will certainly make an engine blow smoke and operate poorly.
I’m assuming your vehicle is a diesel, so it would be worth checking the suction-control valve on the back of the fuel pump, too. Also, a stuck injector that is pouring fuel into the engine can also potentially create these symptoms. I’ve also heard of the Pajero diesel suffering from a build-up of black gunk inside the intake system that can also cause symptoms like the ones you’ve described.
