I guess it depends on what kind of custom ram air you have. I know the stock air box is a little restrictive on air flow. So removing that will give you small gains. Don't expect much of any HP gains from a CAI. Maybe 2 or 3 horse. If you plan on doing exhaust mods, port and polish upper and lower intakes and exhaust headers then each component will compliment the others...but as a single thing I don't think you'll see much improvement over stock. My advice if you want a CAI find the cheapest one you can on ebay or go to your local pluming store and fabricate your own pipe if your handy with that kind of thing.