Engine hesitates and stumbles intermittently

I was hoping someone might've experienced this and knew a few things I could check.

Recently, my car started developing this hesitation that seems to be slowly getting worse. Mostly, it happens after a cold start and intermittently within the next 10-15 min of driving. For a few seconds at a time, the engine will feel to lose power and then snap back to normal, sometimes repeating 2 or 3 times. At idle, the engine will drop to ~500rpm and barely stay running. At cruise, it will simply lose power as if I let off the gas. While accelerating hard, it feels like fuel cut, throwing me towards the wheel.

Sometimes when this happens, the check engine light comes on then off. I checked codes and only got this code and I'm not sure what to make of it. In fact, this code had always shown up for as long as I've owned the car (last Aug). Not sure if the big cam causes low vacuum, triggering this code.
32 - EGR Valve Position/Pressure Feedback EGR Voltage Below Closed Voltage.

If I try to hold the accelerator down during a hesitation, I often hear popping from the engine. I'm not sure if it's out the exhaust or up the intake. I only really hear it from the right side, so I'm thinking intake.

In the last 6 months I've installed a new Mallory TFI distributor, Mallory coil, plugs/wires, and new battery. Mods are in my sig.

I'm not sure what to check. Any suggestions?
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