Originally Posted by Magus2727
Stay with regular.. 89 is not regular is it? That octane will change by region and their altitude. For example in the great state of Utah regular is 85 Octane.
With that long tube header you should be thinking of a tune though. people have observed that they can get some what lean under WOT and a long tube header and free flowing exhaust.
What you're thinking of is with the SVT/Ford Racing header that has been known to lean out at wide open throttle. Most of the headers you find out there really don't cause enough trouble to lean out. But like with any upgrade, it is only taken full advantage of it when you use a proper tune with it.
Originally Posted by kmtalko
ya 87 is regular here in WI and I usually fill up with mid-grade to be on the safe side. I'm hoping it's not running too lean, but I did notice when I pulled my plug wires that white dust was coming off of them which I believe means I might be running lean. I don't drive WOT much, but I really should think about getting a tune. I appreciate the advice.
If you are still running on the stock tune there is no reason to use any other grade than what is recommended by the manufactor. So there is no reason to spend more money than you have to. I would only go up grades if I was hearing "piston slap" or I had felt that the car wasn't running properly on 87 octane.
By the way, Ford recommends 87 octane for our cars.