Yeah I know you can't go by that for a test. I did not see much difference between the silver spring or the purple one. After all this is in a s10 which it does not take much to get it going anyways. I have a quick change on it so I will give a yellow one a try and see what it does. My carb is running a little better so far will have to do some more driving to see how my plugs are going to do. I might have to get another set and am also going to see about getting a good set of aluminum valve covers with good baffles in them from summit so my pcv can quit soaking up some oil.