What manifold is that? The TBI-to-Vortec Head manifolds that I'm familiar with have a passage that is either plugged or connected by a big insulated steel tube to the left exhaust manifold.
The plug would be behind the radiator hose in your photo.
In this photo, the open passage is below the thermostat area, just above the second-to-the-right manifold bolthole.
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The connecting tube would go over the valve cover to the left exhaust manifold.
AC-Delco aftermarket version of the EGR tube.
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You'd also need the fittings that screw into the intake and exhaust manifolds. The left exhaust manifold has two holes, one for this tube, one for the O2 sensor. I did a quick search online, it seems the 2-hole manifold has been discontinued; there's a 1-hole manifold with a boss for the second hole, but you'd have to drill 'n' tap it yourself. GM #12557838, with the two-hole version being 12557838DT (Double-Tapped)
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Without that connection, you have no source of exhaust gas, therefore the EGR
does not function even if the valve opens and closes.