1995 Toyota Corolla Exhaust stuttering

Hello, I have a toyota corolla 1995 that has to acceleration power. The exhaust is making a stuttering noise. I opened the car to see that the timing belt was calibrated properly zeroed out it was. I checked for the tensioner it passed the test. I think the pistons are not firing properly that's just a guess and haven't checked that. Maybe the catalyc is clogged? Like I said the timing belt and system is working just fine. Any help would be highly appreciated I hear you guys are the best! Hope to hear from you soon. Thanks in advance for taking the time to look at my question.