Big Engines with custom exhaust vibrate ???

I'm about to buy a 96 firebird 5.7 LT-1. I test drove it today, but it felt kind of rough when in idle, but as soon as I steped on the gas, that thing
would spin tires. Is this a normal vibration with big motors? The oil pressure would be at a quarter when idling, then half way or a little more when cruising at normal speeds. Engine seemed normal, no smoke or noises. Thanks for any comments since I have never ever driven big sport muscle cars before. Thanks.
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An LT-1 is a small block, so it's really not that big. It shouldn't have a rough idle. It's probably misfiring at idle, which may require an expensive fix. The oil pressure variation is the same as I've seen on my '95 since it was new. Kind of scary, I don't know if they were designed that way. The oil pressure on my 99 Suburban doesn't do that.
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I think Chevy says the oil pressure is supposed to be around 10 PSI for every 1000 RPM. It does look pretty low at idle, but that's normal for the LT1. FWIW my car has a '94 LT1 in it, but I believe it's the same principle for all of them.
John.
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