Just wanted to thank folks on this thread and others that have saved me a lot of frustration (though, I found this too late to save me many dollars). I'll definitely come here first for answers in the future.
OK, first, the saga:
I have a 2001 I30 which I've loved since I bought it new in 2000. Around 100,000 miles I noticed a hesitation when I stomped on the gas. Annoying. Brought it to the dealer and reported it and he cleaned the throttle body. Didn't fix it. I lived with it.
At 103,000 miles I'm in a Firestone for tires and he mentions its time for a tune up. Car was dealer maintained up til now, but it's out of warranty and I figure it's new belts and plugs and what not. Sure why not. I mention the hesitation thing. He tunes it up, changes oil filter/air filter of course... I get it back and maybe it feels a little more responsive... but not much.
107,000 miles. I get home from work, pull into the garage. Park. And the engine stalls. That's odd. Then it did it at a traffic light several days later. Embarrasing. This gets worse and worse. A few weeks later I'm revving the engine at traffic stops to keep the engine from stalling. I take it back to Firestone (cue ominous music).
They say it's the fuel injectors. They clean them (what that means exactly I don't know-- I'm not much of a car guy). I pick up the car and make it about a half mile when it starts bucking and stalling. It's 10 times worse now than when I brought it in. I coax it back to them and say try again. (I know. I'm an idiot. But it seemed smart at the time).
Now it's a new fuel filter, fuel pump, and, oh, we need to drop your gas tank and wash it out. Uh... ok... A couple days (and several hundred dollars) later I get it back. Drives better (a bit). They put a splash of gas in the tank just to get me to a station.
I start to fill up and the pump keeps kicking off. I can't get gas to go in at more than a trickle. <sigh> Back and forth we go and they can't figure out the problem. I'm off to the dealer.
I describe the whole saga to him and get nothing but grief about this is what I get for not letting the dealer maintain it and how they doubt they can fix whatever firestone did and... bottom line I need a new gas tank. $900. Um... no thanks. I'll just gas up slowly.
Oh, and the car still occassionaly stalls. It still has the hesitation. It's grown worse now. Now, when I try to hard accelerate the car doesn't shift up. The RPMs wind up at almost 6000 and just stick there. Sometimes it shifts. Usually I have to let up on the gas before it will shift. It sounds very ill and I feel like I have no power.
Dealer troubleshoots this and says I need a new Mass Air Flow Meter. $500 installed. Yeesh. Guess I'll live with crappy perforance too. I drive home and actually start shopping for a new car on the way home. Figuring this one is about done.
Something yesterday prompted me to google "Mass Air Flow Meter (Sensor)". I had no idea what this part was for. Oh, I do now.
I read the couple dozen posts here about how to clean it and/or replace it. I shopped the sensor up on ebay and amazon ($80). I popped the hood of my car (yeah, about the first time in 5 years or so). Had no idea what to look for. Went to you tube and found a video on cleaning the MAF. Ah, there it is.
It has funky tamper-proof torx screws. Annoying. Oh, well. I went to Autozone today. Found the Torx bits I needed. Found the CRC electric part cleaner stuff. Went home. With much care I reoved the MAF. Two screws, then I had to use a flat blade screwdriver to gently pry the sensor loose. Took it into the sunlight. The wire is caked with black crud.
I held it out at arms length and sprayed it with the cleaner. Waved it gently in the air to get all the liquid out. Wire is bright and shiny. Plugged it back in. And I'm off on a test drive.
Night & Day!! Wow. It's like a new car again. No matter how abusive I am with the accelerator the car just behaves like I'd expect. I actually squealed the tires doing a full accel fro stop. 0 to 60 in about 9 seconds. This car has not behaved like this in years.
So again. Thank you whoever is running this forum. What a wonderful resource. I've actually done my first engine repair in my life with the help of this site.
I've spent around $1,600 trying to get the car right. All of it was apparantly fairly useless. And in fact I now really need a new fuel tank... I don't suppose there's an easy fix for that issue? Eh, I'll live with it. At least the car goes now.
Cost of the actual repair: Torx bits & Cleaner $14. My time: 20 minutes.