I'd say most of the big name brand CAI's are pretty much the same. They all flow well. Big difference is in the look - FRPP looks more stock, JLT is nice if you like the carbon fiber etc.
For tunes most of the "mail order" tunes will be safe and give a good bump. Again, they're going to be dumbed down so that they work for all applications - you get the most power from actually dyno tuning YOUR car with a professional tuner who knows the GT500 engine mgmt system - not just some guy who owns a dyno and has access to SCT tuning software.
Steeda is good - "Best CAI"? Depends on what you're basing that on IMO.
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