Here is what i have learned by experience. I had a coupe with a DOHC KA. I tried different setups and it ran the best with a stock intake box and a 2.5in catback. The cold air intake made my car stall and run funny on the highway and the 3" exhaust killed my torque. Now i have a hatch with an S14 KA, cold air intake, and 3" exhaust. It still kills my torque but im running a different ECU and it solved my stalling problem. Also it runs awesome on the highway.