Why is my 94 LT1 Engine Running Rough??

Hello Everyone! OK, I have had a problem now for many years and am very frustrated about it. I have a 94 Z28 6-speed with a relatively stock LT1 (including good ol'
Opti-Spark). Here's the problem: at light throttle (between 1500 and 2000rpm, all gears), the engine runs rough and almost seems to have a miss. I can feel the car kind of "surging" and it is really annoying. If the normal feel of a smooth running engine were described as simply "mmmmmmmmmmm", my engine would feel like this: "mmm-da-mmm-da-mmm-da-mmm-da-da-mmm". To hide the problem, I end up hitting the gas a little harder, but then it slowly -- and obviously -- accelerates beyond the speed I would like to be at and then have to slow down. I constantly repeat this pattern. My alternative is to pick a lower gear and just get the rpm's up a little higher. In trying to fix the problem, I just had opti-spank replaced (3rd time). Could a vacuum leak be causing the roughness at certain rpm's? Can the fuel pump do this (and how)? The only upgrades I have are a borla cat-back and K&N air filter, and I only have 65K miles on the car.
Thanks Everyone! Steve- snipped-for-privacy@comcast.net
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Possible causes:
- incorrect ignition timing - ignition system operating improperly - low fuel pressure / dirty fuel filter - dirty / clogged fuel injectors
- Camaro Cowboy http://community-2.webtv.net/Z24PODS/2000ccc/
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Ignition timing is not adjustable on LT1's, but problems with the OptiSpark are common, especially if the water pump has gone out. Other than that there is just plugs and wires. On modern cars there isn't really anything to adjust. You just put it together and it works.
Gary

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Sorry... I was speaking in general. I must learn to be more make and model specific. My bad. :-) Check ignition coil too.
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I have a 1996 Z with an LT1 and I had the same problem. My problem was the EGR valve. I read on a message board to disconnect the vacuum from the EGR and if your car runs properly after you disconnect, that is your problem. It was indeed the problem. I replaced the EGR valve and I haven't had a problem since. (about a year)

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