Lifter noises and piston slap are common. Delvac 1 is reported to quiet the engine best, if you can find it. Injectors are loud also.

Google: legacy forum

There are several good ones.

My current Subaru is a '96 Legacy AWD wagon, 2.2L.

'97 and newer 2.2s are interference engines, don't let the timing belt go. Read about the timing belt replacement, lots gets changed. Seals, water pump, etc.

Assuming it is an AWD, check that all four tires match. Read about torque bind. If it is an automatic, change the fluid.

Mine will often throw a code if I click the gas pump one time past full.

The PCV is strange on a Subaru, check it out.

Many of the forum members warn about problems with aftermarket parts, PCV, plugs, wires, etc. It's probably best to stick with their recommendations 'cause it's not an expensive car to maintain anyway.

We always get better than 20mpg, 22-24mpg, and on the hiway we can break 30mpg usually.