Whilst driving the engine lost power and started juddering.

breakdown cover diagnosed that the fuel injector on cylinder 2 needed replacing. They fixed it roadside.

Onward trave was juddery and uncomfortable .

next day the car was incredibly uncomfortable and barely had power. It was pumping out grey smoke quite heavily.

a garage plugged it in to diagnostics and it showed a communication error. turned out erg was unplugged. This was plugged back in and diagnostic run again. No error code was showing. The engine was shaking massively and smoke still coming out. It is worse at 1500 rpm.

no error code and these issues ????? Any ideas ?