At the risk of sounding obvious, it seems that you have something fundamentally out of whack. Upgrading to a higher efficiency evaporator may provide incremental improvement, but I think it's unreasonable to expect it will completely solve the problem if the system isn't functioning at all. Even a bone stock A/C system will provide some cooling. Have you verified that all of your air ducts and your A/C hoses are plumbed correctly? I'm sure you are aware of this, but the A/C air flow on these cars is separate from the heater/defroster system except for the side vents. See schematic below. I'd suggest you first close the side vents and measure temperature at the center vent if you aren't already, as the center vent is 100% dedicated to A/C. I'd be concerned about the evaporator motor relay getting hot. Maybe the motor is overloading. Have you pulled the floorboard and verified that the air path from the inside of the car to the bottom of the evaporator is clear? Are you getting good air flow out of the center vent? Is Griffiths sending you a new evaporator motor/fan with the high efficiency evaporator?
John
