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This guy does a lot of good reviews on fuel injector cleaners. He is not biased and will give you lots of information.
I think the best way to clean an injector is to remove them and have them cleaned, not really a believer in tank add ins.
Liqui Moly's Ventil Sauber is their valve cleaner. I've had good success with BOTH Techron additive and the Liqui Moly Jectron, which is their injector cleaner. I've converted to the Liqui Moly Jectron during past 3 years, based on great success in the Audi A8 with the direct injection system.