Ha, if you have 345hp in a 5.2L Jeep engine, you've already done everything to increase the hp. They come with about 230hp, I have one. Drilling a hole won't effect anything but the noise, you may not pass inpection tho.
To get to 400hp from 230hp would take thousands, get a sports/muscle car if you want to race.
To get to 400hp from 230hp would take thousands, get a sports/muscle car if you want to race.