Best thing to do.. Source a good second hand set of pacemakers for around $500-$600.. then get a twin 2.5 inch mild steel difillipo cat back system for round $750.. and the rest on just getting that pipe infront of your cats opened up to 2.5 inchs.. and that should be your $1500 roughly.. then go get a tune and intake

id recommed an OTR of you can afford one.. roughly $380 - $700 depending on which brand you can afford.. and or plastic or aluminium..
good luck!
P.S. Im still running stock headers and cats on my VY SS S1 with only $770 difillipo cat back twin 2.5 inch in mild steel and a $680 aluminium Higgins OTR and a mafless tune and shes doing just over 300rwhp now

.. Headers will boost you a little but not much imo..