Hi, I'm running a GM 350 TBI setup with a 774747 ECM on a '88 Jeep Grand Wagoneer with AMC 360 and a mild cam. Fuel control only, not using timing control. I've been running this setup for about a year now and everything pretty well dialed in (VE tables, Cold Start, WOT, DFCO, etc). I'm using Tuner pro and have an AEM wideband installed. Because of my cam, I need to run a richer open loop idle . The problem is that often times my BLM will change in my idle cells, even though the ECM says I'm in open loop idle. Sometimes it goes up, sometimes down. A BLM change of just a few points is enough to skew my mixture way rich or lean. Once I enter closed loop in normal driving, it's seemingly random as to when it happens and weather it adds or subtracts fuel. It will never change BLMs while its idling in open loop, and INT is always at 128. If I enter closed loop (i.e normal driving) and then come to a stop and idle it may have dropped down to say 125 or up to 131 etc. Either way, it's really annoying and I've literally spent months trying to figure it out.

Some things I've tried so far are looking at factory 454 bins that have open loop idle and basically copying all settings that have to do with open loop idle to my bin. (I'm assuming that the 454 bins lock their idle BLMs at 128??? Otherwise idle AFRs would be all over the place like mine.) I've also experimented a bit with enabling open loop decel (so I'm in open loop long before I come to a stop to no avail. I have tried disabling DFCO as well no change. It still does it. I've also experimented with the proportional gain settings, O2 constants. I'm honestly at a loss to understand why it's doing this and how to fix it.
Is there any way to lock idle BLMs at 128 or even lock all open loop BLMs at 128? The only way I've found so far is to set all BLM MIN/MAX to 128 but that means I don't have any block learn function in closed loop which is not ideal.

Any help is much appreciated! Thanks!