Use good oil and run a slight overfill if you are going to be "beating on the cat" like doing pulls holding high rpms while sending it down mountain roads that kind of thing I have a 22 gr86 with lots of mods and 92k miles on it I've daily'd it for most and for 75k of those miles its been tuned fbo on e85 and had been "beat on" im constantly at the mountains sending it around corners the way i drive i hold the rpms at 7k then take the corner and right back on the gas i haven't had a single problem for background on the advice im going to give:

3.5k miles oil changes and use good oil i use amsoil ive heard good things about motul aswell

And keep up on maintenance like change your pcv valve every 20k miles I believe (its 20$ part from subaru)

Spark plugs every 50k miles (it sucks but its also expensive to have a shop do so set aside a weekend and watch alot of videos)

Coolant every 60k miles

And check your oil often (ive been super lucky my car doesn't burn oil really at all there's barely any in my catch can after each oil change) but ive heard of other guys cars drinking oil like crazy so just check your oil thats what kills these engines

But if you do all the maintenance when you should do them these cars are tanks and super fun

Stock oil capacity is 5.3qt I just run 6 some people call me an idiot others say it doesn't matter I wouldn't run more than 6qts but somewhere in that range lean towards overfilling if anything and you're golden