Opti, Ignition Control Module, ignition coil, or a burnt plug wire.
More likely the coil. The Opti usually cuts out at higher RPMS, the IGM usually just craps out and the car won't start, and a plug wire only if you recently did wires. Their stock routing sucks ass.
I've seen coils go bad quite a few times on these things, and replacing them is cheap and simple to rule them out.