You only have one cable because you have TCS. Follow the single cable back from the TB up to this inline fuse looking thing. There will be two of them on two different cables. One coming from the firewall going to the TCS module, then another from the module to the TB. I believe you can adjust the tension there. Switching from a LS1 intake to an LS6 intake then to a FAST 90 and NW TB and I have never had to mess with those.
First things first though, make sure you have the throttle cable clipped in the right hole on the bracket. It goes in the hole on the inside towards the manifold. If you are looking down at it, the right hand hole. I have put mine in the left before.