I just found an exhaust leak near the front driver side header bolt (stock headers). There were some signs of carbon blowing out near the gasket on cylinder 1, i got the bolt in another 1-2 full turns perhaps before it was snug.

Can someone tell me what kind of an effect on my freescan logs this would have?
Particulariy where would this "throw off" my 02 sensors the most, if any?
Can it cause false knock?
Any other sensors in the car which may have been affected by it? Thanks for any input...