Toyota Passo smoke problem

AOA all members
I own a Toyota Passo 2007 model. Till last weekend my car was working fine and properly. I have driven my car with no issue from Islamabad to Mansehra. I have not ever installed CNG in it. It is only a petrol variant.
On Saturday, my cousin took car and when he came back, the car was not working. The accelerator was not working and it was shaking. I tried to start in the neutral gear the car started getting race and vibrated. But I was unable to accelerate my car.
Next day I visited a mechanic for my car checkup and he checked the car and told that one engine cylinder is not working. He suggested me to go computerized tune shop and check there. When I went one and there mechanic told that one of the injectors is clogged. He reinstalled it after cleaning with carbon.
Now the acceleration is also still there and car shakes as before. A heavy white smoke starts emitting from the exhaust tip. When I asked mechanic that why this smoke is coming out? He said it is due to clogged injector. The fuel was finished from cylinder. Now after filling fuel it gets smoke again. To fix it, i should fuel up my car 15liters of patrol and then put engine oil of PKR 50 in the fuel tank and then drive around at high RPMs. it will fix the problem. I didnt do it. I really didnt buy his whole story and the solution. After coming back, I went to first mechanic. He replaced the coil of second cylinder to the first cylinder coil and everything was fixed. Now the acceleration of the car is normal.
But the thing which makes me worried is the white smoke. On lower RPMS, there is no smoke and on higher RPMs smoke starts coming out. The mechanic said, the guy used a liquid to clean the injector is reason of this white smoke. In few days, the car will be in normal condition. And the smoke will be vanished.
I should leave it as is? Is this Ok? This will not harm engine o r anything. o r should I change the injector? Kindly help me to get rid of this confusion. o r tell me about a good mechanic/workshop/tune up in Isb who really knows about these cars.