check the LIM flanges, if its got 3m roloc marks, toss it in the trash.
ive had one that was a heavy hand that would have needed rtv around the intake port Oring to seal it.
clean, new single edge razor blades, changed often, the only good way to prep, no need to clean off the "stains" as those are in the metals pores and not above/measurable via a roughness gauge.
3m rolocs are like adding millions of leak paths in 1 second....
if it was ring seal the leakdown would have been notably different from the rest
