Hi, I'm adding a factory AC system to my 71k5 which did not come with AC. I've got most of the interior parts hooked up and working like the heater core, fan, and control cables. I ran into some forums talking about using a FOT (Fixed orifice Tube) instead of the TXV (Thermal Expansion Valve). Some say both will work, but there's lots of talk about using the FOT instead. I also heard a parallel flow condensor is a good upgrade when using an expansion valve. Any AC guru's out there? Is there a big advantage to using an FOT?