Cold weather issues??

A week and a half ago, I was driving my 2003 Range Rover HSE, and smelled oil badly. I pulled over to find my engine covered in oil. Fortunately, I was right next to my Land Rover dealer, and pulled in to have it checked. They determined that due to the cold, a pvc valve had frozen, and wasn't allowing oil to circulate though the engine, forcing it out of the oil cap. I had this repaired. Today I was stopped at an intersection, and an awful smell started coming from my engine compartment. I accelerated from the light, and huge plumes of grey smoke started to come from the vehicle, It sputtered a bit, and I parked it. I checked the engine and there was no sign of anything wrong. I slowly drove the car home, and it was fine, except when I applied the accelerator harder. When I did this, the grey smoke would appear, and the service engine light would activate. The car isn't overheating, and seems to operate fine at lower speeds. Any suggestions on what this may be? I do plan on taking this to my dealer, but would appreciate some knowledge before I do so. Thank you.