You are right about the tires, no doubt. I remember this article....
2013 Scion FR-S Performance Testing With Tire Swap - The Right Tires Make the FR–S Faster – RoadandTrack.com - Road & Track
So what's the big deal about just getting better tires if it will make that much of an improvement in the car? After all, many 986 owners purchase a $500 bearing to keep our cars ten year old cars from becoming uhm, much slower, read stationary, sports car.