Of course there is a difference. That's why your vehicle has knock sensors and an ECU that will pull timing from your shit gas. People putting 87 in a high boost motor (and 20psi is HIGH boost) are idiots.
I wouldn't put anything less than 91 in these trucks. I know the manual says 87 is fine, and I'm sure it is. I just wouldn't want the engine to knock at all and pull timing like you said.
Also, I will only run top tier gas in any vehicle. Home | Top Tier Gas It makes a difference. I've seen it proven on a dyno.