Alright, so I'm planning on doing a custom intake/exhaust/safc2 setup for my GS4. I plan on using the K&N FIPK, and a custom exhaust. What I'm worried about is that I do not want to lean out my car too much to the point of no return.

I plan on getting the Magnaflow 14235, and having piping run to the cat. Now, I wanna do Hameed style as well, with a Tru-X pipe, but I'm not sure if that would just remove the 3rd cat or in fact its just a resonator. I've seen it discussed here on whether its a cat or a resonator. If it's a cat, then I'll just do piping to that. If its a resonator then I'll do a x-pip with custom piping on both sides.

Now, I don't want to get a SRT for the GS. I figure that the SAFC2 will do a better job of tuning the car with both the exhaust and intake, plus its adjustable to any future mods I may also do.

If I was to do 2.5", would that create too little backpressure, and thus significantly decrease my TQ, and require me to reallllllly lean the car out to get that TQ back?

Or would 2.25" be too restrictive and not allow me to get the type of gain's im looking for?

Bottom line is that the GS is my daily driver. I under no circumstance will lean it out excessively. Thus, I'm stuck in between the 2.25 and 2.5. Is one too restrictive, or is the other to free-flowing?

Please help CL