I'm posting this for a friend of mine who doesn't have internet access. He has a '92 SE 5sp with 113k. The car runs good, but occasionaly feels held back. Sometimes, the car will run fine for an extended period and then all of a sudden it feels like the power is cut. The fuel filter and the exhaust (except header) including the catalytic are new. He's thinking it may be the Throttle Position Sensor and/or the O2 sensor. Additionaly, which may or may not be related, the engine taps intermitently. Not like when you run cheap gas, but more like a sewing machine. Again, it doesn't do it all the time, and it doesn't happen only when the engine is cold...it's very random. Could these problems also be caused by some bad injectors?

Thanks in advance guys for all your help!!