Start with Stage Zero. Make sure the car is 100% in tune. Check the plugs, ignition timing, plug wires, cap and rotor, air filter, fuel filter, and base idle mixture.

Once/if your car is in good tune, the next modification would be a camshaft change and possibly an adjustable cam timing gear. The K cam, stock in Canadian B23E motors can often be found for $50-$75. It will increase the mid- to-high-RPM power, with only a slight cost to lowend grunt.

The next restriction is the fuel distributor. A distro from a B23E will deliver more fuel once you've got more air coming in. Otherwise, K-jetronic is a difficult system from which to extract more power without significant mods and expense.

Another option would be to find a cruddy looking, but good running 240 Turbo and swap in the engine and fuel and turbo systems.