Most of the neutrals should be negative. Some of his positives are considered "soft" positives (a neutral or neg in green clothing). Other positives were based on shipping alone yet they haven't installed it yet. I also believe some "thought" it worked but it really didn't and possibly, maybe some really did work, but minimally.
As far as warranty I do not think it would affect it, just as the K&Ns don't affect it. Now if you were looking into a PPC or something of that nature, that DOES work but are typically found to be between $700-$1500+.