dude you need at least 18* I'm telling you
I wouldn't be putting around on 13*, that's for sure.
Anything less than 15* isn't helping.
I'd honestly drop the AFR down close to 11.1~ and see if that gives you a little more headroom. Hopefully at least 16*, even though the 04+ cars have a more aggressive timing curve IIRC.
Amazing what timing can do for you.
add timing until it knocks then back it down a few degrees.