Weird issue after changing my oil?
 

So today I changed the oil on my 1996 GMC Jimmy, just bought and and the oil look really dark before I changed it. I switched it to synthetic and used Penzoil Gold Synthetic 5w30 And a Fram Ultra Synthetic Filter. After finishing up and starting it up, i now smell some type of fumes either it being exhaust, kinda the smell when you start up a four wheeler but way more prominent. Sometimes I smell a slight hint of gas. I also noticed when I go to the back end up the truck it seems to be pushing out a slight white vapor and condensation coming out of the tail pipe. Any help? :/