Split in Manifold Pressure.....Need Help

[cessna02337]

Well.....went to take the aircraft (1967 O-2A) for a 25 Hour Oil Change, noticed while taxing over at normal idle I had a manifold split (Front engine reading 16, Rear 14). Briefed mechanic, during oil change he found a small crack on front engine manifold, left side. Removed and replaced along with the correct gasket. Taxing out, for maintenance run, same issue, no change, still had the split.

I performed various engined runs at different power setting and it seemed to follow at all ranges (about 2 inch split, front engine always being higher). I have a Shadin fuel / air data computer and fuel flow to RPM seems to be within .08 per engine fuel flow in gallons per hour. when RPM matched.

Looked at a video I shot last flight to confirm previous matching of manifold pressure and noticed my Manifold pressure as I remembered were always EXACTLY matched to include during taxi/ground ops as well flight.......any info regarding next steps, haven't flown it yet, planning on a test flight Thursday.

From what I was told, this is within the maintenance limits, just don't like the split as I have never seen before.

Thanks as always in advance, T.