'93 S-10 Blazer, 4.3, very low oil pressure

Engine is the "W" code Vortex. Has AT and is 4WD, has 130K miles. Just had this thing in to have fuel leak fixed within the intake manifold. Don't know
details on what was fixed, or what exactly was leaking. Invoice doesn't show anything beyond gaskets and shop supplies, so maybe it was just a leaking gasket??? I know it wasn't the injector - had that done a few years ago, and my bill was too low for that to be the problem.
It had bad mileage, poor performance, was missing badly, and smelled of raw gas. Took the shop two times to get it done, but that problem is fixed. I did learn that they had a new guy working on my truck, and that he left a vacuum line disconnected when putting everything back together the first time. That is why it took them a second time to get this fixed; they had to completely undo everything that was done to get to that disconnected line.
Now my problem: it has a very bad knock now, and it has very low oil pressure. The pressure was marginal at idle (15 psi), but would go up quickly when given some gas, approaching 40 or so. The theory given to me was that the fuel from my leak had washed out whatever gunk and other accumulated stuff was helping the main bearings keep pressure up, now causing this new problem. Wasn't a big deal short-term, but would have to be fixed long-term.
On the short 3 mile drive home from the shop, the knock got very bad, oil pressure wouldn't go up at all, and the "check gages" lite flashed on a couple of times. Killed the engine, coasted into the driveway (it's downhill), and am now waiting for the tow truck to show up to bring this thing back to the shop. No way am I firing this mother up again till somebody from the shop is present.
My question: the fuel leak causing the bearings to be "flushed" seems like a reasonable theory, but is it actually BS? Did the new guy cause me a problem in the bottom end somehow during his work on the top-end? I didn't have the low pressure problem before bringing it in to have the leak fixed, and I sure as hell didn't have the nasty knock it exhibits now. I understand the very basic mechanics of what is going on, but have never done this kind of work before. Helped my dad years ago with valve lifters, de-carboning pistons and a bunch of top-end work, but never any bearing, crankshaft or other bottom end work.
Appreciate your advice and help.
Jamie C.
Cincinnati OH USA
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Check around the intake and see if there is silicone sealer squeezed out. It is possible that the fuel thinned the oil and caused crud to block the oil pickup, or excess silicon could do the same. I would take it back and tell them to fix it.
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Steve Williams
Near Cooperstown NY
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Repair shop has it and is working on it. I'll post an update when it's done.

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