97 Blazer rough start Dies

Hello everyone!
I've had my blazer for a few years and I am approaching 120k in miles. I did a tune up (Spark plug wires, plugs, rotor and cap) at about 85k.
I just replaced the fuel filter. When I start up the beast, sometimes it runs fine, sometimes when the idle comes down from the start, it shakes and dies. Lately, it has been shaking and dieing, so I give it gas for a minute, and that solves the problem temporarly.
I tested the fuel pressure and it is around 55psi running. I havn't yet busted out my GM mechanical books to verify the normal operating pressure. I was suspicious of the battery considering it is about 2 years old and I recently installed an elaborate sound system, but I've been monitoring the voltage and it is normally not below 11.5V when I attempt to start and the problem is still occuring.
No engine light as of now.
Ideas? Throw them at me!
Thank you!
Kory
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Fuel pressure specification is 60-66psi. Resolve this concern first and re-evaluate. Also check for moisture accumulation in distributor cap (Don't see it much in V6, more commonly seen in R code motors where blocked dizzy vent screens permit moisture accumulation and heavy corrosion, but it's a free/easy check).
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Are you sure about that voltage reading? That is low. You probably already know that 12 volt auto batteries are not really 12 volts when fully charged. They are well over 13.5-13.7 IIRC.
The reason I mention it, we used to have a Fiero that regularly ate alternators and when the voltage got that low, the ECM would make it run rough as heck. At some point, it stopped running totally.
Your car could well have other problems, but that voltage just doesnt look good enough.
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I fixed the problem~ It was the IAC valve. I just sprayed it with some Carb cleaner and brushed it a bit and it is as good as new!
Thank you for your contribution!
Kory
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