You do know that he is talking about the 2nd gen IS right?you can get header, exhaust , intake and cam gears and tune it, thats what gives u the most hp.
Also u can get a SAFC to maximize ur power.
Intake - AEM, INJEN, K&N
Exhaust - HKS Drager 2 (one of my favs)
Cam Gear - AEM, Unorthodox, Fidanza, Titan.
Header - Mazzuri, HP Racing aka Toyomoto, Megan Racing and Xerd if you can find it.
The answers, respectively, are maybe and no.is it illogical to purchase mazzuri headers for the 350 if its a lease and is there any way to install it and keep the car legal?