Idle/ cruising misfire issues!

So It really has taken this long to try and sort out, I had found I had TWO bad powerboards, so I swapped an entire new socketed smec and that took care of the 5k cutout. Car pulls pretty decent, verified with boost gauge and secondary vacuum gauge and that fuel pressure rises with boost as it should and at idle.
and really has no issues with a load on it, No cut out in boost, AFR perfect, But all my issues now are poor idle/ misfire that ONLY seems to happen when below 10inHg of vacuum, at idle itll pop, miss, sometimes the vacuum will oscillate a few inHg's but that's it alongside the idle drop. (smells like its almost loading up on fuel when it does this, and could be a rich misfire to so speak? When cruising, itll have that same popping/miss which to me sounds kinda like a detonation event, but again only when its below 10inHg. I have swapped valve springs, camshaft,tried a few different calibrations/tweaked a few different ones, Performed cylinder compression and leakdown tests, Got 125 all four and less than 10% leakage on all four. Swapped intermediate shaft, distributors, caps, rotors, plugs wires, all of that. Cleaned, and even added MORE engine grounds. The only thing I have NOT done is swap out lifters, those are PT lifters and shims and haven't found much info or anything similar to causing any known issues. When I was swapping valve springs I had the rockers off and all the lifters felt pretty solid, couldn't compress any of them by hand. This car only produces about 17 inHg of vaccum peak, but the mechanical tests seem to all indicate its a non issue. Also have swapped my 95 lb injectors for 52 to make sure there wasn't any issue there.

2.2 CB, G head, 52mm TB, Holset HX35, AEM 400 fuel pump, -6an feed and return to 12 gal fuel cell. 1989 turbo van SMEC electronics, socketed SMEC running an OSTRICH