I try get my plugs a brown color...Tan is a scary color, I've seen 4-5 jet sizes difference to get the plug to go from tan to brown, but when it does, it happens in one jet size.......In other words, you could go from a 240 mian to a 280 main and not see any difference in color, but when you go to a 290, it changes a lot....thats what makes the tan color so scary....Find the dark brown color..