Me again, sorry about all the questions guys! Just keep coming across more parts I need. (Can you tell it's tax return time?

) Anyways, where would you guys recommend I get it. I would think it's necessary since I'm jumping up to 4.10's. Thanks..........again!
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1997 Cobra (Black on black), C+L 80mm MAF, K+N filter, Pro 5.0 shifter, BBK Springs, Taylor Wires, 2 Chamber Flows, ASP Pulleys, BBK off road H pipe.