Nissan 240sx engines are very flexible powerplants. Just changing the tuning chip alone in the master electronic engine control module (ECU) will boost your horsepower from the standard 155 at 5,600, and 160 pounds-feet of torque to 269 horsepower for an investment of just $69. If you want to go all the way to a completely turbocharged motor with a kit like the KA224de where you will not only be swapping out the engine chip for the hotter chip, but adding a turbocharger and all new hosing and stainless plumbing to make it work. Plus, with the right pressure waste gate, you ‘ll find the investment is in the vicinity of $3,100 (discounted). There are many other kits for this engine as well.
For more info, see Four Tips for Buying a Used Nissan 240SX