I'm relatively new to the S550, but I remember that the computer for the S197 was marketed as being extremely sensitive, so much so that any changes to the intake required a tuner.
Frankly, you're planning on spending $1500 on parts, and for all the benefits that you're going to get from tuning - better throttle response, better fuel economy, more efficient use of the intake and exhaust parts, increased time, MORE POWER - spend the extra $400 on the tuner and a good tune. My S197 was so much fun to drive when I had the intake, exhaust, and tune installed, and was, quite frankly, boring when it was returned to stock. The last month, after I had it appraised for sale, and was waiting for delivery of my 2016, was just sad.
2016 Race Red GT Premium Fastback - Performance Package, Navigation, Enhanced Security Package, Ebony Premier Trim