You can't. Unless you pull and install the 155 hp engine. The horsepower is made internal. I'd have to look into the specs to tell you the exact parts but it's usually a change in stroke, piston, valve train or some other internal components.
You'd also have to change out your entire electrical system. The 4-TEC engines use an "EMS" (engine management system). This is specific to your motor. It takes in all the sensor input and with the MPEM (multi-purpose electronic moduel), makes changes to your engines electronics for optimal operation. So, to change the motor means to change the electronics too.