FI gets the most post love, AAM is also a great shop. I have their axle back with a NISMO H pipe (lets call it frankexhaust) and am pleased. Could be a bit louder but I prefer less loud over more loud and like the deep exhaust note over the mid-range rasp that I hear on all the FI set ups (could be because of TPs etc...). HFCs would wake it up but I have kept mine stock due to not wanting the natural hiss and I don't want to deal with a sensor CEL.
Both companies make quality parts, great welds etc...as noted its then subjective. To my ear the AAM setups are a bit more pleasing then FI based on my tastes.
Its good to have choices
- b