photo credit: Power 106 Memphis native BlockBoy JB stepped up to the L.A. Leakers Freestyle to check in with Justin Credible and DJ Sourmilk for his first appearance on the coveted LIFTOFF series. BlockBoy swagged out a 2008 classic by spitting over Lil Wil’s “My Dougie” track rapping, “Walk up on the set, steppin’ with…