Q's about fuel injector and head gasket problem

[jsr20det]

I have a 90 fastback which I plan to sell. Main reason is because I have a big smog problem. It eats a tremendous amount of gas, pollutets like a factory, and stinks up the place with a gasoline smell. I replaced the o2 sensor and there is no difference. I had my friend who is a mechanic take a took and he said that my fuel injectors are really dirty. He suggested that I use some fuel injector cleaner, I had already used them before with a gas treatment mix, so i told him i already did that. Then he said that I need new injectors.

A friend was with him also and he said that it could be the injectors, or it could be a blown head gasket. I am thinking about fixing the problem if it will cost me under $200. The friend suggested that I swap in a KA24DE motor in there. I have a couple hundred that I could roll on to swap in the DE motor. How much would the the swap cost? I just need the engine alone right? Also, how much would new fuel injectors cost me? How bout the head gasket? I got alot of rust that worries me on the car, should I be worried? is there anything I can do about this?

Sorry for the wave of questions but im just really concerned and looking forward to being one with my car again. Comments/advice/opinions all appreciated. Thx in advance.