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2001 4.8L Silverado throwing lean codes.

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Old Sep 11, 2011 | 11:16 AM
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Default 2001 4.8L Silverado throwing lean codes.

My truck keeps throwing codes P0171 and P0174 which is lean condition on both banks. For the past week it wouldn't want to move when you touched the gas especially after it had been sitting but would get better as it warmed up. It would also hesitate under acceleration and wouldn't move at ALL when you mashed it. Naturally I assumed it needed new intake manifold gaskets after doing research (and having friends with Chevy trucks) so I replaced those. Truck is driving AWESOME now. Acceleration is back and it drives great, but for some reason the codes keep coming back and it still has a tiny bit of rough idle. Seems to be idling at 500 when it used to be at 600.

Any ideas what I should replace next? I check for vaccum leaks and couldn't find any. Truck is bone stock.
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Old Sep 11, 2011 | 11:39 AM
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Have you checked the o2's with a scanner? Also, a bad or dirty MAF can cause those issues.
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Old Sep 11, 2011 | 11:44 AM
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I've had one where the manifold itself began to seperate. Check that out. How many miles?
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Old Sep 12, 2011 | 07:45 AM
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Fuel psi is??
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