I just added the xl-18 to mine, a local dealer had it in stock, it definitely made a big difference with all the gears, but 2nd is still notchy when cold once in while. It is better though.
Custom ordered 2012 Mustang GT Premium, Kona Blue, 3.73 rear, MT-82, Over the Top White Stripe and Optional 18" Polished Wheels. Built on Jan 4th, 2012.
Added: 2013GT Splash Guards, Ford GT Strut Tower Brace, MGW Shifter, Raxiom Smoked Aero Tail Lights, Moroso Air/Oil Separator, J&M Extreme Joint Rear Lower Control Arms, Infinity Reference 8602cfx speakers (x4).