2001 Chevy Lumina Sedan Hesitation

Yeah, its just that. I jumped in my car to come home this afternoon to grab a multimeter to help a friend diagnose an issue with his truck(a chevy of course). The trip to my house was normal, I didnt notice anything wrong. I shut my car off, ran inside, grabbed it, ran out, maybe took 5 mins tops, and started car up. Started normal, everything looked good, no idiot lights came on or anything. Nothing out of the ordinary, untill I backed out, and proceeded down my block a ways. The car had pep (like always) till about 2000 RPM's (yes I have a tach), then it kinda stayed at the speed, and so I pressed the accellerator down to get going 30mph through town, and it kept at 2000rpm's, and slowly climbed, till it hit 3000, and then shot off (almost as if it finally realizied it had been floored). I immediatly knew something was wrong. This kept up at every stop I had to make. It seems to take a split second to get from idle 800rpms to 2000rpms, but maybe 3 seconds to get from 2000 rpm's to 3000rpm's. catch what I'm saying? Also if i have it in park, and I rev it, it revs just fine, it winds right up to that 4000rpm govorner. Anyways, I got to my friends house who only lives across town, and wouldnt you know it? he found his problem just before I got there. So I had him jump in and check out my car. The dumb thing seemed to drive good with him in it. go figure. So, later on, I went out and it was doing the same thing. I filled up with gas, because I was at a quarter, and I put gumout fuel injector cleaner in it. That stuff seemed to help out a little (or maybe its in my mind), but this problem seems to point to the throttle position sensor to me. I also thought maybe fuel filter, and plugs and wires. Any ideas? I bought this car used with 39,000 miles on it, and now it has 55,000. I doubt anything like that has ever been changed, i know I never have, and was wondering if maybe I should? whats regular intervals for that stuff? I did however put a k&n air filter in, and yeah, it did help considerebly I thought. Oil has always been changed at 3000 mile intervals or less, and I did have the coolant flushed. Any ideas? Also, back in winter when it was really cold outside, I would start my car, it would start great, and I would let it warm up for maybe 5, 10 mins, and when I got in it to drive it, I would notice a subtle "miss" that seemed to go away as it warmed up, or as I drove it for a few minutes. It only happend when it was cold, and since it always went away, I thought nothing of it. Maybe these two issues are related? Thanks for reading, and any info would be greatly appreciated.

oh, yeah, by the way, its the 3.1 V6, or maybe better know as the "3100SFI". (For those of you who reads whats on that intake plenum.)

First and foremost, change that fuel filter. Mine still had the factory one in it at 90K, and it was a bit choked up, but not causing any problems yet. But I've seen them go bad earlier, I think the recommended interval is like 36,000.

I thought TPS too when I read it, You should be able to use your meter to test ohms as you slowly sweep the throttle open and closed, and watch for any drop-outs.

If the filter or TPS is not the cause, I'd need some more info to make an informed guess.

Like, when you pressed down on it, but weren't getting a reaction from the motor, I'm assuming there was no intake woofs, backfire through the intake is indicative of very lean condition.

If that happens, you can assume that the throttle opening is being read correctly, but the fuel is not being delivered for some reason. If not, then I'd think the ECM didn't get the message that the throttle was opening, for whatever reason.

I myself think it was a bad batch of gas. After I ran it a little today after filling up last night with the injector cleaner, today it runs as good as ever. I am however gonna do plugs and wires, and fuel filter, just for the heck of it. Thanks Jeff.