Will K&N cold air kit improve '03 S10 performance?Kevin??

I know such has been asked before; & I read ONE supposedly independent study which verified such a kit DID help, I believe a Jeep product--15 added hp or 15% better fuel mileage, or such. I've got an '03 S10 w/4.3 Vortec and automatic transmission. Operates as one should. But if a K&N kit would help, I might install one. I'm sure when a product advertises they guarantee "up to" a 20% improvement, all they are saying is that you can sue them if it improves MORE THAN 20%!!! And if it improves NOT AT ALL, then, that is within their warranty's parameters--i.e., 20% or less. Anyway, I'd love to hear & read some true experiences. TIA, s