The worst carburetor problems are ignition problems.
Ignition is cheap; vital for the car to run and priced to that effect, and is often the first thing where problems arise. Replace plugs, plug wires, maybe your dizzy cap and rotor/ignition coil. Basics like that. Also, make sure you have a working vacuum advance since it supports acceleration at part throttle or off idle.
If it does come down to your carb, they're relatively easy to rebuild once you finally just pull the trigger and dig into it. If it is carburetor-related, what you're describing sounds like lean spots or lean stumbles. Quadrajets are not tuned to run rich like Holleys are. That's why they get such a bad reputation compared to a Holley; which can run a freakin' weedwhacker right out of the box because they deliver so much fuel. Quadrajets on the other hand were application-specific, and in your particular model year, they were all tuned and calibrated to run on very lean mixtures to satisfy strict emissions requirements. Lean-tuned carburetors are picky, finicky carburetors that are only meant to appropriately meter fuel for the exact engine they were meant for on the production line. With today's more volatile, watered down fuels (EVEN "pure" REC-90 fuel is still formulated differently than fuel from the late 70's, and btw that is ALL you should be putting in your fuel tank if you're still using the QJet), this problem is even worse. In fact, spark plug reading is sort of a pointless venture these days because of modern fuel.
If your car has performance modifications, even as simple as a true dual exhaust or headers, then it requires modifying the carburetor. The increased scavenging effect of headers and a true dual exhaust, along with the removal of severe restrictions such as the catalytic converter and even the heat riser valve, will cause the engine to run leaner and so the quadrajet will require larger primary jets to meter more fuel, as well as thinner secondary metering rods to do the same thing for the secondary system. Air bleeds also play a role, which are orifices drilled into the Quadrajet casting that provide oxygen/air into the emulsion mixture - the larger the air bleed, the more air is in the fuel mixture. Late model Chevy trucks used Quadrajets with very large main air bleeds which makes the fuel mixtures very lean even after upping several jet sizes, explaining why those Qjets are hard to modify. Luckily, most of our Pontiac carburetors have relatively benign air bleed orifice sizes, so usually enrichening by means of larger jets, thinner metering rods, etc. will provide more fuel to satisfy the requirements of modifications such as headers, camshaft, etc.
Idle system is another beast on its own, which should be the FIRST thing you satisfy before moving onto the primary/secondary tuning. Very aggressive camshaft profiles will not provide sufficient idle vacuum to support a stable idle unless you turn the idle speed screw in a lot, which the more you do that, the more you risk breaching into the primary metering circuit and leading to what is known as "nozzle drip." This is why if you have a very aggressive camshaft, modifications to the idle circuit are necessary such as larger orifice idle tubes, opening up the idle down channel restrictions, and even enlarging the mixture screw ports may be necessary.
All of this and more is described in Cliff's book as referenced above. I've learned so much about Quadrajets thanks to him and have opened mine countless times. You just have to take that first step, because once you have it disassembled... well, then you really have no choice but to reassemble it if you want to drive the car again. That's when the learning begins.
