zerohour had a popular post and tried a lot of things on his Subie. Here's the thread:
https://ecomodder.com/forum/showthre...-5l-14034.html
Those older Subarus are tough to coax more fuel economy out of, especially the automatics. I sold a 2007 1 month after ownership partly because it got terrible fuel economy, and partly because it handled worse than my 1996 Legacy.