Moderate to heavy smoking does considerably impair any kind of tissue regeneration, no matter if muscles, organs or penis. We are talking at least 1/2 speeds here if not 1/3.
On top of that, smoking constricts blood vessels which obviously impairs PE and poses greater risks for the wrong kind of damage.
I also smoke, but only a few cigarettes a day and only 1/4 the regular strength. I try not to smoke at least 2 hours before PE. I feel it really makes a difference how well I can push it, with slight good pain the days after, and much less discoloration and that kind of stuff.