When I rev my car, I get a squeeking noise. It squeeks once when I rev up and once when the rmps drop back down. It also does it from start when I take off and sometimes when I switch gears. It only does it when the car is warmed up and I drove it for a little while. It is annoying. It started after I put on my Header and Exhaust. The only thing else that is new is the spring bolts that hold the cat to the down pipe. I just got them from a muffler shop. Any ideas of what this could be? Could non-oem spring make noise? Any thoughts?