Butane inserts totally defeat the main advantage of a Zippo, wind resistance, and are therefore no better than a $1 generic bic. Plus they are a total PITA if you're left-handed, as the flame can only come out one side, so if a lefy holds it so he can work the striker with his left thumb the flame shoots out back toward his hand, not forward over the pipe!
If you can taste the fuel, either a)you aren't giving it a sec to burn off, b)you're holding the lighter too close to the pipe rim (1/2" above minimum, more with a fresh fill), or c)it's all in your head.