I fitted a Cobalt to my 12 plate Sport Black. It takes a thousand miles to fully obtain the finished sound which is just right for me. It makes it sound like a sports car. Whether your son prefers more “whizz, pop, bang” is another question.
Oddly, the only drone is at 1500 rpm with the top down. Motorway cruising and general hooning around is fine.
Don’t reuse the old crush washer or use liquid gasket. Use the one supplied in the box. Beware of rusty and/or welded flange bolts if fitting yourself.