Is 3" exhaust to much for a 318??

Get some tailpipes on it,go down to 2 1/2 or 2 1/4 and tell the muffler guy not to weld it together that you might want to change it later,that's all just sh oot for the (I can change it later if I dont like it) the tailpipes will wake it up.you should go for the 2 1/4 pipe with what you have or smaller just save the big stuff for just in case