I have a 2004 Civic Si w a K20A3. Is there a simple ECU re-program that will get me near 200HP?

Or can an RSX K20Z1 be a replacement? If so any major mods needed?

 

First question: NOT A CHANCE.

Second question: Yes, you can install a K20Z1 in place of your powerless K20A3. Use your complete intake manifold except for the fuel injectors... use the ones from the Z1 engine in your original fuel rail. You will need either a KPro installed in your EP3 ECU so you can upload a Z1 tune/basemap OR an '02-04 Type S (PRB) ECU and have the immobilizer re-programmed to your key and column. Everything else bolts up. To get to 200 "Wheel" HP, you will need a header and cold air intake... and a cat-back exhaust will add a couple ponies on top for good measure.