okay guys, I have to get to the track, but I need to know if I should switch up my plugs first. See, I have GT40 Cast iron Heads, I have TF55 NGK Plugs, these are a step colder than what the NGK manual says I should be using with the GT40's, (actually I looked up what the cobra uses and it said the TF45's I think). But I was wondering if stepping up a heat range will make any difference... these are the same plugs that were in the car when I bought it and it ran good, so I don't know if I want to mess with it. Anybody? I need to know so I can get it fixed ASAP. Thanks