Perhaps maybe the head gasket is a little tired? Readings on one and two are close enough to make it a possibility but the remaining cylinders 3,4 & 5 are pretty good and consistant as well. Just a coincidence perhaps? I would do a coolant test for presence of hydrocarbons and perhaps an oil anyalisis as well before concluding too much. Might also pay to watch coolant for any bubbles while running. Remember that head gasket is probably no spring chicken. Also I might suspect a little weakness in the gasket between cylinder 1 & 2 where the gasket bridges the common point between the two cylinders. In that situation would not expect any other symptoms particularily. I think it a possibility only because 3,4 & 5 seem so equal and one and two are low but equal as well. Kind of would expect to see more unequal compression values across the board in general in a worn engine. Hope others with more experience on the 617 will comment.