I would have to differ...
I bought my ebay SRI (link 1) last year, and it did a great job, but I wanted a CAI. Seeing that the injen was $200+, I didn't want to dish that out, so I was the first (I THINK) on this forum to go ahead and buy the ebay CAI and I must say that it doesn't add a difference in performance, but looks and sounds REALLY NICE!
My opinion... go with the ebay CAI... it's only a few more dollars than the SRI. Ask ANYONE who bought an injen and an ebay CAI, they're almost exactly the same, except for the INJEN sticker...