I just charged my A/C - it's converted from R-12 to 134. I only used 5 12oz. cans of freon. 350 with front and rear air. High side pressure is 250-260 with the engine and compressor running (A/C on max and rear A/C on). Low side pressure is running 90 with the engine off. The low side presure seems a little high to me. Anyone know what the correct readings are and why mine may be off?