I would check your downpipe for leaks. I had an ultimate downpipe that i bought used from someone on this forum, i thought it was normal, but then one day i pushed my car to 7k rpm and all of a sudden my car got really loud. My downpipe had broken.
The next day i had no choice but to drive my car with a broken downpipe. As i was driving to work the next morning, i lost power steering, my steering wheel got really hard, Once i got home i jacked my car up and noticed that the broken exhaust had melted the power steering wires and fused them together. I had to separate each individual wire and wrap each wire in electrical tape, luckily it wasn't a big problem and i temporarily fixed it. I went ahead and purchased a brand new Skunk2 downpipe and the exhaust sounds soo smooth now, i have no more leaks.