Originally Posted by FuszNissan

I have had the FI 18" with CF cans + HFCs and they sounded mean.
1. Are you going to lower your car, because you may scrape with the F.I.
2. Do you mind having some drone at lower RPM's? But having killer sound in the higher RPM's
3. The quality of the work, and welds are amazing.

I have the AAM 2.5" Version 2, but I am Forced Induction.
1. They look stock
2. They will have more clearance if you are planning on lowering your car in the future.
3. Less drone, nice sound (not overpowering)

I really like both, but if I had to choose, I would go F.I. just for that pure raw sound. I can't explain it, it's beastly.

The AAM with TT's sounds amazing as well, but that F.I. just has that high note.

I hope that helps a little.
They are both great systems.