Throtle body spacers work best on carb and tbi motors. Contrary to claims made by the people selling them they don't do a thing for Vortec motors. They do make a good base for drilling and tapping for nitrous fitings. With that said, look at the throtle linkage, maybe you have to bend the mounting bracket at the throtle body. With the emgine turned off, try bending it until there is just a little slack in the linkage, then bend it just enough to take the slack out of it. Sometimes this has to be done on the vortec engines after the intake manifold gaskets are replaced, and the braket gets bent, while its being worked on.