wow a 20-40hp gain with no s/c, that's going to be a challenge...

you can start with this

-make an intake
-180* t-stat
-zzp plog
-get a tune
-Hv3 insert

Id say with those mods you would run a mid to low 15. You could do a d/p but, i don't think you would benefit much from it... tuning it is going to be a whole other issue with your year...