You can do get the star achievement as well if you save after defeating Adam
1. Complete all of Panam Palmer's side-quests and unlock the Life of the Road Trophy.
During Nocturne Op55N1, head out onto the balcony with Mysty and talk to Johnny Silverhand.
2. Select: "[Call] Panam."
Select: "Just need a minute."
Select: "Somethin'... I gotta do today."
Select: "Gonna ask Panam for help."
Select: "Take Omega Blockers."
3. Complete We Gotta Live Together.
4. Complete Forward to Death.
5. During Belly of the Beast, defeat Adam Smasher and interact with the Alt AI.
6. Select: "Body's Johnny's. I'll go."
Enter the Cyberspace.