On the 4th Gen Legacys, Subaru lowered the motor even further, down between the frame rails, so you've got an angle caused by the height of the frame rail versus the height of the spark plug hole. And the valve cover and the frame rail are so close together, it makes it difficult to get a ratchet between the two. Some have made it work without a u-joint - I did, but I had to buy a thin-line ratchet. My 2nd Gen LGT is a lot easier.
If you're doing this on a 2.5i, then it's possible the alignment heights are different from the 2.5LGT so you may not need the u-joint. Take a look at what room you have to work with and determine your access angles. And read this thread - lots of good suggestions in it for changing the angles.
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