head back exhaust 2002 H6

Has anyone done this? I can't find much about it. If i were to have custom heads, and a dual H-exhaust made up would it be worth it? I'd have to remap the ecu i know to get best results. I was also thinking an H type exhaust in instead of a Y pipe and would lower restriction (probably wouldn't even have cats. we don't have emissions checks, and compared to the diesel trucks the rednecks drive meh on environmental impact) and might end up hurting performance instead of gaining? I'd adapt a EJ25 intake to make a ram air or something like that.. or just custom build it with the current one and some cutting.

I read a EZ30R had the 3" intake valve, and i notice all the tubing on my EZ30 is 3" on in the intake lines, so does it to have a 3" intake valve? Exhaust and intake really seem to be the only ways to improve this motor horsepower wise, so does all this seem logical?