904 won't go into passing gear...

Not sure what you mean by gas coming out of the linkage. When you are messing around with the linkage on a carb and the engine isn't running it's not unusual for a bit of gas to start leaking out around the throttle shafts. Every time you move the throttle a bit the accelerator pump squirts some gas into the throat of the carb. If the engine isn't running the gas tends to pool up on the throttle blades & will leak around the shafts. I have even seen it seep out under the carb on occasion.