Ummm why wouldn't it be the stock one?
Do you have an aftermarket CAI (even then very doubtful it supplied a different MAF, I don't know of any)?
Odds are it's the stock MAF sensor. There are very few applications that will require a different one.
Heck I have a stock one......
2007 Mustang GT Vista Blue 740RWHP/motor 904RWHP/spray 9.01 @ 152 mph 1/4 mile, 1.40 60' 2008 Clash of the Titans World Finals Champion 2009 Strictly Street Points leader/ET & MPH Record Holder 2009 GT500 Grabber Orange Vert 594 RWHP 11.5 @ 120mph it's my slow car!