i've had cars come into my shop w/ clogged cats or clogged mufflers doing that. too much backpressure on the motor and it cant really rev. check for flow out of the tailpipe to see if you have good flow. if you feel hardly any air coming out, you may have a situation. you can also try unbolting the cat and leaving one bolt holding it to the exhaust. if the car runs fine with the cat unbolted, it's probably a clogged cat.