i just had 2.25" on my stock 240 with any tip and it sounded pretty good although. I don't see the point in putting an exhaust on a car when it won't make any power gains(mine came with an exhaust, and I hate the noise so I put a stock muffler on.), but to each his own. I'd go for 2.25-2.5"

3" is going to be too big for a stock N/A KA and will probably lose torque