i have a one inch spacer on my built 350 it has to gaskets top and bottom how can i tell if one is leaking because i know air fuel mixture is off but im hearing different opinions and i don't want to take it all the way a loose if that's not it the motor and everyhing in it is new it might be a year old now so any help i would appreciate it.

With the engine idling, spray little shots of carb cleaner at various points around both the upper and lower gaskets. If it's got a vacuum leak the idle will pick up and smooth out momentarily when you squirt where the leak is.