its not all that hard to make good headers.mimic the $4000 ones out there for mercedes.youll allmost allways be paying 80 -90% in RD and name.what kinga primaries 1.5 1 5/8 1 3/4?should see bout 5 -15 with any decent set but the main part will be getting high flow or all flow to integrate with youre tune,or should i say retune.you should lose bout 20 lbs and need the o2 sensor bout the same spot,not to have to needlessly lengthen.