I wouldn't get hooked up on the engine and power thing, it can eat you up sometimes and stop you enjoying the car.
Your Z is a real beauty and on todays cluttered roads its getting harder to stretch a cars legs. The main thing is you love the car, you got it looking they way you want and its already turning heads and will be a conversation starter at the pumps. To me thats the full package.
All cars have their unique sound, V8's, V10's, 6's, boxer engines also four pots can sound gorgeous. Think Caterham, Lotus etc, sound amazing (Lotus using Toyota engine from regular car!!). Go to a British touring car race, phheff those four pots sound amazing. Do some research on exhausts and yours will sound like a beast, I love the sound of four pots!!