morning starts,smell of fuel

its on my 03' yukon 5.3 125k miles,,,,every start in the morning,it smells bad like fuel...ill rev it up and it throws a cloud of white smoke sometimes black.

i recently switched from 87 ranch gas...to 93 octane,im wondering if that has something to do with it.also added a magnaflow exhaust:ugh2:

what do yall think?anyone have this problem?

white smoke is usually condensation. Black would be overrich condition usually caused by a leaking injector at shut down.

thanks man,yup its white!!