17 Sti mods help.

Hey guys I’m a big car guy I grew up with race cars n used to have a 700 hp cobra , but I always loved Subaru’s and always wanted one. I have worked on plenty but never got deep into modding to much. So I got a 17 Sti which I love it came with a invidia q300 catback, cob cai , n I think it had a downpipe before me. When I got the car it just felt to quick but who am I to complain lol. So let’s get to the mods it has a set of unequal headers n up pipe to keep that sound please n a catless downpipe, and a cobb accessport when it got installed I saw a previous tune my guess a stage 1 ?
but I spoke with a few die hard Subaru guys because I was in fear of cobb n there bs I was told what to pay attention to on my accessport gauges , my airfuel is deadon the money like everything else. But I checked my oil the other day n itis burning some oil now this isn’t a big deal i know with a turbo car n a ots tune that is basically just dumping fuel.
i have read some posts on oil I use Mobil 1 with motul engine protect, I wondering what u guys think? And should I run a range colder plugs a lot of people are saying yes with my mods n that they will helpto keep cylinders cooler. I am doing my plugs because I am getting a little studder at idle after a race the other night I know what some think that it might be ringland but I know what this looks like n sounds like the car does not studder or miss at all when driving normally n at idle it goes away sometimes I have had this before with Subaru’s. Oh n the car does not smoke at all. Oh and I keep having one stupid problem I keep blowing my uppipe gasket at the 3 bolt on the headers Side n the bolts come loose I’m about to go n get a 3 inch collector gasket from advanced auto a reusable one that’s thicksoft metal n get some locking nuts.Thanks my Subaru bro’s. N I just got a 06 legacy gt that I wanna do a Sti manifold swap eventually. What do u guys think the best E tune is for my Sti I don’t have money for a real tune yet.