Are you throwing a check engine light? What is your mpg now?

 

Why would your really even need a tune for a gear swap? Besides just to correct the speedo to the new ratio. I personally bought a used Diablo just to correct the speedo when I had 4:10's installed. Went ahead and installed the "93 octane performance tune" while it was hooked up. Mods are K&N fipk, bbk 75mm tb, C&L elbow, o/r x, welded in 2 1/4" 40 flows, 4:10's.