If your talking about your 05 GTP, you'd want a 3.6.
And upgrading injectors is not needed at that point in time, you wont outflow them.
I am talking about the 05 GTP. What kind of gains am I going to see out of this? My dad has a stock 09 Mustang GT and loves to remind me that he does, so I want my GTP to crush his little pony
05 GTP. K&N Intake and magnaflow mufflers, plog-cross-rear exhaust with 3' DP. (Soon to be 3.6 and ported SC)