Hey guys, im new here. My throttle body got stuck so I went and bought a holley sniper efi 102mm one to replace the one I have. Now my truck won't stay on and idles crazy. Can anybdy tell me why? Does it have to be tuned? Also my throttle cable seems like its stretched out. Cable tightens as I press the pedal and then it will pull the throttle open. Can that be an issue also?

This is my old throttle. Its a 2001 ls1 block with 243 heads, 102mm throttle body, t56, 6 speed trans. I bought the truck like this so i have no info about the build.

 

Tuning will be 100% necessary.