tecchris, i think you're on the right track. it looks like you have the wrong piston size.there's no way you would have 74# suction and be low on gas with a return air of 73 deg. the piston is too large, not allowing liquid to back up into condenser for subcooling.install a t.x.v. and charge by subcooling (6-8 deg.) then set your superheat.but, make sure the t.x.v. is not commercial,must be for residential with off cycle bleed port.or,find out the correct piston for the cond. unit.