This is really frustrating. PO had replaced the evaporator, compressor, etc. There is a slight leak somewhere, so I need to add r134a every two months or so.
The question:

The compressor cycles normally on start up - 45psi, kicks in and 22psi, clutch disengages. As the engine gets hotter, the cycle times get longer. After about 5 minutes, the pressure stays at 25psi, the compr4essor engaged, and slowly starts to creep up; but the temp at the vents also gets warmer.
I sprayed cold water from a hose onto the right side of the radiator and the pressure dropped to 22 and cycled again. As soon as I stopped the water, the pressure started to go up, and the compressor stayed engaged. Yesterday, after 30 minutes of driving in stop and go stuff, the pressure was at 45 with the engine running and hot.

If it indeed is the plugs keeping the exhaust too hot, which makes the intercooler (radiator) hot, which plug range should I go to?

As a side note: while driving, when the ac cycles, the car noticeably decreases/increases engine speed to the point where I am adding gas when the compressor engages and decreasing at disengagment.

Klaus - better too wordy than not enough.
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98 V70Rawd(108Kmi), 95 854T(88K mi), 75 164E(173K mi)