Hello!

I'm currently tuning in closed loop, and I've been experiencing some surging issues that I can't seem to resolve, and would like some guidance if at all possible. I've recently completed open loop tuning with everything running great, and no surging whatsoever. Here's my specs in my 88 GMC truck:

- 7747 ECM
- Vortec 350
- xr258hr cam
- 1.6 roller rockers
- 454 TBI/68hr injectors/ 30 psi fuel pressure
- nv3500 manual trans
- shorty headers

I've noticed in closed loop, it surges in very specific places - light throttle driving(specifically at low speeds), and at idle while revving the engine and holding the pedal at any rpm below 2500. I've been combing the threads for the past weeks, and it seems like most people point to either proportional gains, or INT - Delay. I've tried messing with these tables, and while it does change the feel of it slightly, the surge isn't eliminated.

So far I've reduced the PRP - Gain vs O2 Error table by multiplying by .625, since I've increased the fuel pressure and injector size, and that seemed to help drivability quite a bit. I was getting surging at idle in closed loop, so I reduced the timing at idle, increased the idle speed to 700 rpm, and went with a heated O2 sensor and that pretty much eliminated my idle surge. To deal with the idle - rev/light throttle surge, I subtracted the PRP - Gain Multiplier vs Airflow table by half, while increasing the INT - Delay vs Airflow table, and it changed the light throttle surge slightly. Instead of it bucking/surging really fast in some places, it surged really slow while I was holding the pedal steady, almost like I was slowly pushing and releasing the brakes. I'm attaching a datalog to illustrate what I'm talking about. This specific datalog is me holding the pedal at around 6-12 TPS at idle and it shows the surge while I'm holding it steady. Any help is appreciated!