Car Problem?

and my exhaust is restricting the air flow, but every since i replace my 02 sensor, it has been acting up, so i think i got a bad 02 sensor

so which is the problem? the bad o2 sensor or the stock exhaust restricting air flow?

I recomend getting a tyfoonmotorsports.com air filter the mesh on the cone on the top is very light and air can get through it alot faster.

which air filter are you talking about on that site?




and also..i just got my AEM underdrive pulleys intalled...and things seem to be getting worst...can't hardly get to 75-80 mph..
but i did felt a gain in the low end torque...it could be the lack of air coming out..since i have stock exhaust..or might be a bad o2 sensor.