I feel he is just pushing a sale, The plugs you are using will work just fine. I have used cheap plugs to expensive plugs and everything in between. You will notice slight difference between them. They will also change slightly if you use a hot or cold plug. Is this a shockwave correct and not a BB with a two speed trans. Because the two speeds will do this if the transmission is not set up correctly. It's like the trans is in 2nd gear the whole time.