Truck Repair: 2000 Silverado problems, mass air flow sensor, fuel pressure regulator

Question
Hello Van,
    Thanks for the quick response.  I live in Juneau Alaska where the prices are high and there aren't a lot of choices so unfortunately I'm kinda at the mercy of this guy.  I did mean the Mass Air Flow Sensor.  He initially told me that the fuel pressure was 65 psi at idle and dropped below 51 psi when the gas pedal was depressed.  After that didn't work (although he said there was notable improvement of course) he said that he found the fuel pressure regulator seals bad and that he couldn't just replace the regulator, he had to replace the entire system with a "spider" system.  I questioned this because he did say the day before that the injectors all passed the leak-down test.  After I got it back last night and it was still bucking, I called and raised some hell and he took the truck back in this morning and swapped out the plugs, cap and rotor again and now it seems to be running well.  I'm not sure if he did anything else because the all that stuff was fairly new.  At any rate, he didn't charge me for the tune-up so I have a feeling he knows he's been giving me the shaft.  I have the truck back now and it seems to be doing all right so I'll just cross my fingers and go from here.  Thanks again for the info.  
John

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Followup To
Question -
Hello Van,
  I have a 2000' Silverado, V-6, automatic, regular cab short box 4x4.  My problem started a few months ago.  The truck seems to be mis-firing.  It started out just occasionally and slowly got so bad that it finally threw the code for multiple mis-fires.  I did find some arcing from the coil wire so I replaced it and insulated the new one, but it didn't seem to completely fix the problem.  I've had it in to both a Chevy and GM dealer.  The Chevy dealer swapped out the MAS and then decided it was the cap/rotor.  I swapped those myself and it didn't fix it.  I then went ahead with new plugs, wires, coil, air filter and TPS.  Although it ran better, it still didn't run right.  Just got it back from the GM dealer and he first decided that the fuel pump/module was bad ($1015....) didn't fix it, then he replaced the entire fuel injection system ($565) and although he said it was fixed, it wasn't.  It ran bad on the way home and I just dropped it back off to him this morning (reluctantly).  I am back to where it is missing mostly when I am slowly accellerating.  It is no longer throwing the multiple mis-fire code, but it is definitely still bucking and mis-firing.  It seems to idle fine and seems to run at WOT fine, it's the "in-between" throttle positions that are causing it to happen. At idle if I just barely touch the gas-pedal, it will start to miss.  Any help will be greatly appreciated.  It's my wife's truck and she's bogarting mine until her's is fixed!

Thanks!
John
Answer -
Hello John,
That dealer is reping you bad.
For one thing, those prices are way high, and for another thing, those things should not be replaced without several tests to actually pinpoint the problem, and verify it.
He is just guessing at possibilities, and swaping parts at your expense.

If the EGR valve hasn't been cleaned, it is possible that it is not seating properly, or is opening at the wrong time, possibly due to an improperly routed vacuum hose.

I assume by MAS, that you mean MAF, the mass air flow sensor. If not, then the MAF may be dirty. But it can be cleaned, rather than just replace it. Same with the EGR.

I assume since he replaced the entire injection system, that the injectors and the fuel pressure regulator are new. Has the pressure been tested?

Van

Answer
Hi John,
I spent a week in Dillingham, and prices there would just kill me.(Or maybe I could make a fortune?)
Anyway, glad you finally got it right.
Hard to say...he could have adjusted the timing just a little different, or something.
Hope it stays fine.

Thanks for the update.
Van