89 GMC Sierra

It was -40 degrees this morning when I started my 89 sierra to warm it up before work. As I was walking back inside I though I heard a small ping from the engine but thought nothing of it. The truck seemed to run fine on the way to work but the check engine light came on half way there but went out when below 40kph. Then after work when I went to start the truck it fired right up but seemed to put out alot more exhaust than usual that was darker and smelled of gas. There was also a black spray from the exhaust which also smelled of gas. When driving the engine seemed slow to respond from a stop and when slowing to a stop the truck seemed like it wanted to stall out. The truck is an 89 sierra 1500sle with a 5.7L 350 auto