I used OEM gears (AAM) and I had to open up the ID of the pinion shims because they sat on the radius from the pinion shaft to the gear. Before I noticed this I was at about a .023 pinion shim like you. Then I noticed the shim getting bent like a countersunk washer by the pinion radius. After I opened up the shim ID I ended up with a .034 pinion shim. Also if you truely have factory GM gears they run much tighter BL when initially set up, BL spec is like .004-.006.
1994 Trans Am, M6 hardtop, hotcam, SLP mids, Strange S60 4.10