Hi, i've just got HKS air suction kit, re-amemiya header and amuse catback exhaust for my 2008 rx-8. I've also got full veilside bodykit and wing, and 20-inch andrew baccarat rims.
However, after all the installation, the car seems to go much slower than the standard one. During standard, it could reach 243km/h and 0-100 in 6.7 secs.
Now, my car only manages to reach 186km/h and 0-100 in 9secs.
Is this normal? I know it's heaver but i think this 186km/h and 9secs stuff are too ridiculous to believe.
I've reset the ECU but nothing changes , or do i have to dyno tune the car?
I really need you guys advice here..
Thanks...

first make sure everything is connected as it should

Then,

cap the nipple behind the throttle body.

Then install a Ram Air duct for your HKS

using VFAD with any short-ram intake is asking for trouble.