It doesn't fall on it's face in the upper rpm's like the 3800 does. Pit your average bolt-on modded 300 crank horsepower 3800 against against a Grand Prix GXP and the GXP will pull away every time.
Generally not with the modded stock rockers but as the cars age it's definitely smart to change the valve springs.But you need valvetrain mods to make 300bhp... even if it's just 1.9s, right?