Help - 2001 Blazer knocks while accelerating or going uphill

I have a 2001 S-10 Blazer with about 60k miles. It recently started knocking while going uphill or while accelerating. It almost sounds to me like a diesel engine. Otherwise it runs fine. Its seems to do
it a little worse just after the first start of the day. It may be coming from under the hood but it almost sounds like its some exhaust thing. I tried using a tank of 93 octane gas instead of 87 and that didnt seem to help (only maybe a tiny bit).
Anyway, Id prefer not to spend a bunch of money if its something I can do. Does anyone have any suggestions where I can start looking.
Thanks. PS
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It could be a exhaust leak in the manifold. Check there.
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Did you happen to notice what the oil pressure was when it started knocking?

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"Paul_S" wrote:

Check EGR valve function and knock sensor too.
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