MSDS supposedly adds 12-15HP, Y-pipe is good for about 8HP w/cat 10HP/with out.
Comparison for dollar per HP goes to the Sho-Shop. Headers are over $600 + a hefty install fee or about 6-8hrs in your garage for install time.
Aluminized w/cat is $249 No cat $149. Add to that your getting 15% off and only paying $10 for shipping!
Nick, c'mon just do it and be # 20
