Dealer says it is because the independent mechanic I get service at does not add the Subaru additive during a flush and fill and encouraged me to use dealer for service. I can't afford the dealer. Is there a secret additive they add during a flush and fill that a regular mechanic would not know about?

hanger and the baffle. Will need a new center pipe and muffler/flang Cost $1082.

Can I get it done with Subaru parts at none Subaru shop?
Is Meineke Car Care Center in Norwood Good? Or is better to pay more and use Subaru?
How much do you think they will charge?