Auto Racing: mini stock problems, chevy cavilar, vacuum gauge

Question
I have a 83 chevy cavilar 2.0. the motor was rebuilt. it is now 30 over. i have a situation when running the car. i have a brand new holley 2bbl 350 cfm on it. 3 weeks ago i ran good .. the week after that i would come into the corners and i let off the gas just before to burp it and then push gas and car would not pick up or go shall i say  i would pump pedal to get it to try to go but it would still not get up to speed. when i pumped pedal and came around corner it would pick up speed but i would then again have problems with corner. so last week i went back and i hd same problem not only in the corners but on straight away to. i would give it gas and it would seem to go and then a second later die down so i would start pumping fuel pedal and still go for a sec and same thing.? what could be problem... has to be something with carb.? the jets are at 65 still ... the carb bowl when lookingat it from front of car is facing or sitting on left side toward fender. ..  the spark plugs i looked at are black to really dark brown...   what should i do... please help..

Answer
Kind of a tough question, when you mentioned your plugs I'm going to assume that you looked at them from time to time before this problem and they looked OK.  Here's my train of thought based on that assumption;
   Take a little time to eliminate your fuel system; fuel pressure good?  Should be 8-10psi, holleys are also prone to push fuel over the top if there's too MUCH fuel pressure, remedy this by installing an in line pressure regulator.
   Be sure your air intake system is unobstructed, nothing binding or moving it while the car is moving. With a vacuum gauge check the vacuum off the intake manifold, you should be pulling a steady vacuum, 15-20lbs, main thing is it's steady and doesn't fluctuate up and down in slow wide sweeps, that would indicate weak valve springs or a cam rounding off.  You have good fresh fuel?  I'm skipping over this a little fast because in light of how you described it running fine and now running worse I'm actually leaning towards a non fuel problem.  Ignition problems will often be masked by rich carbing, which happens every time you mash the pedal and the engine gets a shot from the accelerator pump.
   Carefully inspect your wiring, plug and coil wires, etc, and see if it could be loose, pinched or near moving parts where it could be grounding out in the corners.  I once had a similar problem I could not for the life of me diagnose until I discovered a wire that would ground out when the car was dipped in the corner.
   Aside from the possibility of too much fuel pressure I'd guess ignition especially because of the blackened plugs.
   My only other thought is could you be getting oil into the fuel system through a pcv valve in the corners?  You can install an open breather on top of the valve cover to keep excess oil from building up in the valve cover.
   Give these ideas a looking over, and then get back to me and describe anything else that may have changed, ie did you have an accident, change anything else?  Is it backfiring and if so is it coming throught the exhaust or through the carb.  ONE OTHER point about holley carbs is; if you do have a backfire though the carb it can easily blow the internal power valve if so equipped, and it'll run poor until replaced.  If it's equipped with a power valve, there's an orifice available that'll protect the power valve.