I started to hear a difference in the car(96 SS) that I think is a header leak. It's pretty much normal sounding at idle when not in gear. But when under load while driving I can hear the phht, phht, phht type noise while accelerating. It's not very noticable while cruising but you can still hear it's not quite smooth like it was before. The long term fuel trim for bank 1 is running about 7-10 higher than bank 2 and the O2 readings for bank 1 will go down as low as 25 sometimes. So does this sound like a header leak on the driver's side header? You just can't hear it while standing next to it and revving the engine and I see no signs of where the leak is. I'm pretty sure I'll be taking a look this weekend but want to make the best guess at which side it's coming from.