I do have a general pep article stickied at top of this section you should check out if you havent.
I wouldn't pin them at same time , I would do MGF and give it around 1hr before pinning lr3 imo. but you could use both.
Personally if I where going to stack something with igf 1 it would be a ghrp2/mod GFR (1-29) combo.
Have you used either of these before?
Ran igf1 and cjc/ghrp from RUI and it was a nice run. I did use mgf with it once also but I didnt really notice anything extra out of it, but I also only used it because a friend gave me some extra he didnt want ( didnt like pining so much so said fuk it lol)