'05 5.3l mysterious misfire

[LSXapache]

I've been trying to diagnose what feels like a slight misfire in my lm7 for awhile now. At idle you can feel it and see it if you watch closely, also the rpms drop slightly when it happens. It happens continuously but not in any kind of pattern. If the rpms are increased you can feel/hear it almost in a rhythm of running right, rpms drop runs poorly, running right rpms increase, etc. Can't feel it at cruising speed but can at idle and during acceleration. Acceleration isn't smooth like it should be, and it takes a slightly longer time to crank than it should. Does it in open and closed loop. Throws no codes. My torque app shows the fuel trims to be normal but slightly rich(+4 is the highest I've seen it go), no misfires detected. I realize torque app is no tech2. The exhaust is slightly black indicating a rich condition. Engine is stock internally, LT headers, Cold air intake, Frost tune, modified factory wiring harness, this powertrain sat in a wrecked truck for about two yrs before I purchased it and did my swap.
Things I've checked or tried:
New o2 sensors
cleaned MAF
new intake gaskets, also checked for vacuum leaks everywhere multiple times
New knock sensor harness, and cleaned the valley area of dirt/corrosion
fuel pressure stays 55-60psi
Fuel rails/injectors pulled and engine turned over to verify all were spraying
new ngk tr55s, plugs all looked the same(slightly brown porcelain, black soot on the rim of the threads, new wires
compression is 180-175 on all but one cyl which is 155-160
pulled valve covers and inspected springs and pushrods

I'm running out of ideas and have exhausted searing google, ls1tech, etc. Will a tech2 show misfires that the torque app will not? I feel like unless I have away to pinpoint it to a cyl or verify its a random/all cyl misfire I'm never gonna find it. Also read that I may need to do a crank relearn, or the misfire detection could've been turned off in the custom tune, waiting to hear back from frost on that question.