I'm looking to buy a used Jenvey ITB kit tomorrow and seller was kind enough to check the flatness on the engine/gasket side.
The question now though is I really have no idea how good or bad this is.
Top and sides looks good I think with max 0.04mm (0.00157") but the bottom is 0.16mm (0,00629") at the worst places.
I got a used intake manifold gasket and with a simple caliper I measured the thickness to around 0.25mm so maybe 0.16 isn't so bad?
Here's a couple of pictures with the measurements.