Pontiac Repair: 2000 Firebird Problems - HELP!!!!, vacuum leaks, pontiac firebird

Question
I have a 2000 Pontiac Firebird V6. I have had this problem since I bought this car brand new.  It hesitates when accelerating.  It feels like I'm running out of gas and with every gear shift, it gets worse.  It jerks over and over again.  It usually (but not always) works itself out around 50 or 60.  The major problem is that it is intermittent and I never know when it will act up.  I took it in to the dealer a few times when it was brand new and they wouldn't even look at it...they said it was bad fuel.  My Dad is a mechanic and can't figure it out.  Everything has been changed: spark plugs, wires, ignition module, fuel filter, oxygen sensor, catalytic converter, and the transmission has been worked on.  I was told once by a body shop worker at GM, that it felt like an electrical problem to him.  However, it doesn't do it all of the time.  And it never triggers the check engine light, so they always say that there is nothing they can do.  I wonder if it could possibly be a bad computer.  Something else I've noticed is that sometimes when it does this, there is a knocking sound that accompanies it(not always though).  I'm not sure if that has anything to do with it.  I NEED TO KNOW WHAT IT IS!  Please help me!

Answer
Hi, have you tryed to pull up a code on it? It will set a code if the engine light don't come on. Check for a bad ground wire in the ECM, check for vacuum leaks, check the antiknock sensor. If you have not done it put a higher octane gas in. Also may need to check the timing.