If you have the engine out of the car and don't mind time then you can make it make a little more power but it's not usually worth it on N/A units, turbo is the way forward.
some simple suggestions are to port match the whole motor and polish the intake (inside) etc etc its been done to death, I have only tried all this stuff once and I put hundreds of hours into a 3SGTE which is turbo powered and I am not sure it made any difference...