The port that is low in the engine bay in front of the compressor is the high pressure port and the one that is closer to the shock tower (also on the driver side) is the low pressure port.

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1986 300E (3/2002) Rear ended and totaled (10/2009)
2000 Xterra (5/2000)
1992 400E (11/2009) -Sold
1986 300E (12/2009) - Sold
2004 E500 Wagon (6/2013) - Sold