There has been a bunch of chatter about alleged lip-synching on this tour (most notably from Eddie Trunk of all people). I have yet to see anything definitive despite a bunch of grainy YouTube videos proclaiming the smoking gun. If I had to speculate, I'd guess some of Paul's screams and yelps are augmented in order to spare his vocal chords. Big deal. I could care less either way, as I still enjoyed the spectacle. If I wanted vocal virtuosity, I'd go and see Adele (who probably uses more backing tracks than KISS).
I think it's funny that a lot of self-proclaimed KISS fans are utterly disgusted by the alleged lip-synching. Isn't it kind of like a life-long WWE fan seeing a grainy YouTube video of a blatantly missed/faked drop-kick, and declaring "That's it, I'm done! Wrastling used to be legit, but I'm not shelling out one more dollar for this garbage!"