Maybe his Silverado has mods - don't know. I've never driven a non-SRT Crossfire, so I can't say.
I did have a 2001 Silverado Z71 regular cab w/the 5.3L V8. I think it had ~285 HP stock and I put a Jet chip on it and used a Hypertech PowerProgrammer on it. It was fairly mean - for a big heavy truck.