Truck Repair: Truck has NO power, throttle position sensor, fuel pressure regulator

Question
I have a 2001 Chevy S-10 3 door pick-up truck with a 2.2L 4cly with P/S, P/B, A/C and a 5 speed manual trans. with 143000mi on it. The other day on my way home from work I picked up my truck from the park and ride lot. Vehicle started normally but when I drove up the freeway on ramp I noticed a shortage of power. The engine made a real funny noise, kind of hard to describe. Sounded kind of like when the secondaries open up on a carbureted car. But I wasn't going anywhere. Didn't overheat, didn't die when you let it go back to idle. Idled fine. But when you push on the gas and get it up to 2000rpm the rpm starts to fluctuate. Down to 1000rpm, back up to 2000rpm and so on. It makes that noise (secondaries opening on a carb car) the whole time. It will never go past 2000rpm. Oh, I forgot to add that there is NO check engine light warning and that the tail pipe is clean as a whistle. So what ever is coming out the tail pipe is cleaning it out as it passes through. There used to be a black like soot on the inside of the tail pipe.I changed the plugs, wires, air filter, and fuel filter. No effect. I've never had any trouble with this truck in the past! Any ideas as what could be wrong? I can't afford to take it to a mechanic right now, especially with the holidays approaching. I would appreciate any help I can get! Thanks!  

Answer
Hi Joe,
The first thing I would do is connect a fuel pressure tester, and see what the pressure is. Low pressure can be caused by a dirty filter, a bad pump, a fuel pressure regulator problem, or a leak in the fuel lines inside the gas tank.
If the pressure is normal. then I would test the throttle position sensor.

All of those problems could exist without setting a code.

Van