If there are gasoline drops it is because there is a leak, it is necessary that they look at the hoses of the tank, and those that reach the engine to the filling tube of the tank, the technician who checks you that has not noticed a tiny leak, sometimes it happens that the smell is caused by the packaging of the fuel cover where the fuel battery is damaged or runs Cover is under the rear seat, the inspection is relatively easy, because you only need to lift the rear chair and see if it is wet around the lid, if so see where a technician to solve the problem because they require experience to fix it.
As for the work of only three pistons for the black smoke you comment, it must be that an injector stayed, that is to say open and flood the cylinder and this stops working for this reason is also the black smoke; I think the loss of strength should also feel the vehicle, right? I hope to help you something