I think after the workout's shower is the best (wait for the body to cool al ittle) because heat can degrade the peptide. injecting pre or post and showering can waste away your IGF.
don't buy IGF for pumps, use creatine or nitro stuff. IGF is much stronger and better than that. furthermore, IGF-1 pre may abolish some of the GH response during workout.
when I did IGF-1 I worked out mornings or early afternoons and did IGF post shower. that way it also didn't mess with my night time GH response.