Trouble at high RPM?

[blue00gt]

I bottomed out hard about a week ago (don't get me started about the crappy roads around here) and I noticed yesterday that I am developing an exhaust leak between the passenger-side header and the H-pipe. I didn't get a chance to fix it yet, and now when I tach it it will not rev past about 5200rpm in 2nd gear. You can keep the pedal to the floor and it just does not accelerate anymore. It doesn't make any funny noises or buck at all in 2nd - it feels like it is running smoothly but it just won't rev any higher. As soon as you upshift it goes again like it should until you get to high rpms again. At the top of 3rd and the bottom of 4th I heard what sounded like pinging. There is no check engine light on. Could the exhaust suck enough air through the leak to mess up the O2 sensor and cause the computer to try to compensate? There is no check engine light on.
I plan on fixing the exhaust leak this weekend and then if that doesn't fix the problem I'll take it to the dealership. Anyone had any experience with a problem like this?