These cars are geared pretty conservatively, so I doubt it's an issue; mine doesn't pull very hard in 5th either. Essentially, to increase acceleration, you either need to increase engine torque (which can go as far as your wallet will let you), or increase your rear gear ratio (which is usually the better "bang for the buck" mod here).
Most people recommend a 3.73 gear set for these cars (with manual transmissions), and having driven one, I can say the difference is quite impressive. I have yet to do the mod to mine, mostly because I spent more than intended on
suspension a few months ago. It's definitely on the short list though.