Sorry to hear you bought into these problems. Take this as a learning experience. Never EVER buy a used car with unknown mods and conditions, and especially one that has the Engine light on. That was extremely foolish of you. Ok enough of that.
Personally I would return the car if possible. If not, you need to at least get tuned for the current mods. Then save up to replace the short block. Oh and ditch the turbo timer.