Strokers CAN hit higher RPM's, but they are actually worse at it than a modified 4.0. When you stroke something, you increase the amount the piston moves up and down. You have more momentum in the system, which means it is harder for the pistons to change direction. If you rebalance the crank and such, it'll rev nice. Look at diesels; they are the ultimate strokers... Strokers make gobs of torque and a really well balanced one will spin up.