My daily driver 87 csx. The only stuff not factory stock are MP LM, roller cam, and no cat.

The issue is intermittent, but occurring more frequently. When accelerating, the car stumbles, barely accelerates, and pops out the exhaust. To me, it feels very ignition related, because of the exhaust popping. Yesterday, it blew out a sooty loud bang, so I'm leaning towards ignition or possibly over fueling. Under hard acceleration, it will produce boost and accelerate better, but not like it's normal potential and it's popping and miss firing the whole way. Suddenly it stops and drives normal.

No codes have been active. Tach, vacuum gauge read normal during this (not bouncing around) No other instrumentation is present.

So far I've tried from a known good 88 shadow a coil, pick-up coil, complete secondary ignition system. I have a drb2 and I'm seeing no values out of the ordinary, I've looked in the fuel pressure regulator hose for fuel, none found. I bypassed the baro read solenoid with no changes, double checked cam and ignition timing and they're correct.

I don't have another LM as a tester, as most of my stockpile is smec based

Any ideas? Other things to check or try?